#help-17

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grand frigate
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I don't know where to start.

ornate ember
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the larger function subtracted by the smaller function

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and where the intersect is your bounds

wary bolt
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Hi, I have an algebra question, at least I believe it is

grand frigate
ornate ember
ornate ember
grand frigate
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that would gice this no?

ornate ember
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yeah correct

grand frigate
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is that possible?

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if it's too advanced, i'll probably just get back on this problem in the future.

ornate ember
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just curious, what course is this for?

I don't know if I grok what you're asking for. ๐Ÿ˜ฆ

Can you highlight what area you're actually lookin for like you did above?

grand frigate
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it's just the area of the curve and the x axis - the area i highlighted.

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.close

vocal sleetBOT
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ornate ember
vocal sleetBOT
#
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woven jungle
#

could someone help me with this problem? honestly i have no idea what im doing rn

high frost
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this is asking you to find the second derivative of f(x^2)

vocal sleetBOT
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@woven jungle Has your question been resolved?

woven jungle
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thank you so much <333

vocal sleetBOT
#
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silk ember
#

Yo

vocal sleetBOT
silk ember
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Lemme take a pic real fast

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,rotate 270

twin meteorBOT
silk ember
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Technically the question is a physics type of question

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but it isnt part of physics class

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nor have I taken physics before

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Its more of a figure process physics thing for engineering class

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So my question is about the conversion

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The equation PE/1 โ€ข 1/m โ€ข 1/deltaH = g (considering PE = m * g * deltaH, and that I need to solve for g)

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And g needs to be in ft/s^2

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on the left I replaced J with kgโ€ขm^2/s*2

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and on the right I replaced J with Nm

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So either way

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I'll get kgm in some sense

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but I feel the right side is easier to understand my question

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So if I take out the m

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I have 901N

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then I can replace N with kg mass and to 1m/s^2

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so I was looking at how I can change / get rid of lbm and I was thinking

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if I switch N to kg mass, is that the same as lbm?

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so I could convert pound mass to kg mass

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and would that cancel out or would that leave me with a kg/mass answer?

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Honestly these problem sets with units are out of my repertoire so I really struggle with them for some reason

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Actually better yet

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if someone could explain to me the connections I'm missing with lbm and lbf that'd be nice

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because I feel those are a bit confusing to me

vocal sleetBOT
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@silk ember Has your question been resolved?

vocal sleetBOT
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@silk ember Has your question been resolved?

vocal sleetBOT
#

@silk ember Has your question been resolved?

vocal sleetBOT
#

@silk ember Has your question been resolved?

vocal sleetBOT
#
Channel closed

Closed due to timeout

Use .reopen if this was a mistake.

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Available help channel!

Send your question here to claim the channel.

Remember:
โ€ข Ask your math question in a clear, concise manner.
โ€ข Show your work, and if possible, explain where you are stuck.
โ€ข After 15 minutes, feel free to ping <@&286206848099549185>.
โ€ข Type the command .close to free the channel when you're done.
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vital latch
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sorry last trigonometry question i promise

vocal sleetBOT
vital latch
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so if we have sin(2x) = cos(x)

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i got help before to say sin(2x) = sin(pi/2-x)

quick estuary
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or you can expand

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sin2x

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using double angle formula

vital latch
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yes! i saw a video on this just now

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and i was wondering

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if i do this

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3x = pi/2,
x = pi/6
quick estuary
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not a general solution

vital latch
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i think you can do this though

quick estuary
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if it asks general solution then no

vital latch
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3x = pi/2 + 2'pi'n
x = pi/6 + 2/3'pi'n
quick estuary
#

2npi/3??

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thats incorrect

vital latch
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no like (2/3)pin

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i think

quick estuary
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same as what i said

vital latch
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๐Ÿค”

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ah wait

quick estuary
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for n = 1 you will get 5/6pi

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which is wrong

vital latch
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i wrote wrong i think

quick estuary
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ye

vital latch
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or no i didnt

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nvm im so confused

quick estuary
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your first line is wronf

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wrong

vital latch
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because we have sin(2x) = cos(x)

quick estuary
vital latch
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which we convert to sin(2x) = sin(pi/2-x)

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and then we can move the x over and get 3x = pi/2

quick estuary
#

it can also be - pi/2

vital latch
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and then we have 3x = pi/2 + 2 pi n

quick estuary
#

thats a part of the solution yes

vital latch
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so x should be pi/6 + 2/3 * pi * n for all solutions no?

quick estuary
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no

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because you have not taken

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the solutions from 4th quadrant

vital latch
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ah ok yeah

quick estuary
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3rd

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i mean

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not 4th

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where both negative

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this answer you got from both positive

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for the other answer

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i would not the substitution method but

vital latch
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ok so the better way to do it then is to do

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sin(2x) = cos(x)

quick estuary
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2 sin x cos x

vital latch
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2sinxcosx = cos(x)

quick estuary
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sin x =1/2

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yep

vital latch
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move it over

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2sinxcosx-cosx = 0

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cosx(2sinx-1)=0

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cosx=0 and 2sinx-1 = 0

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cosx=0 gives x = pi/2, 3pi/2

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sinx = 1/2 gives x = pi/6, 5pi/6

quick estuary
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ye

vital latch
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and then on that we have to add 2'pi'n?

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' being *

quick estuary
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u can use union

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or not use 2npi

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instead

vital latch
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what would the union look like? i thought union only was a thing in graphing when expressing the range/values?

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although I guess this is values too

quick estuary
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2n+1 pi/2

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this is always a solution

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and

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ok

vital latch
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oh yeah because you ust add 2

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and get 3pi/2

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but the other one is not the same no? because pi/6 + pi would give 7pi/6?

quick estuary
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yea its not

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union i was talking about was

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one solution is 2n+1 pi/2

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other is n pi +(-1^n) pi/6

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because when n is even

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we are adding pi/6

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when its odd

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we are subtracting

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if we get that we use this form

vital latch
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okok

quick estuary
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i cant seem to think of a way to write them together rn

vital latch
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its fine

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but if i were to do it the way i did it originally

quick estuary
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youll miss solutions

vital latch
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at that point i would have to not only do sin(2x) = sin(pi/2-x)

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but also

quick estuary
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5pi/2-x

vital latch
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cos(pi/2-2x) = cos(x)

quick estuary
#

no thats same thing

vital latch
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and then in the unit circle look for where those values occur again?

quick estuary
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you would have to do 5pi/2

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to get the 5/6 solution

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and for pi/2 and 3pi/2 uh

vital latch
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couldn't I just say that sin(x) = 1/2 which also occurs at 5pi/6?

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and the same for cos?

quick estuary
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your equation wont support that tho

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this is what you know

vital latch
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or no it's gonna equals the same thing

quick estuary
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but your eq says 3x=pi/2

vital latch
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ok yeah

quick estuary
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so its not convincing

vital latch
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in that case

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if you got this question

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sin(3x) = cos(2x)

quick estuary
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just expand

vital latch
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what would you do then?

quick estuary
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this is. ๐Ÿ’€

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convert everything to sin

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you get a cubic

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find its roots

vital latch
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but sin(3x)

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is not equal to 3sinxcosx

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right?

quick estuary
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its not

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its

vital latch
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that's what i suspected

quick estuary
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3sinx - 4 sin^3x

vital latch
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wait what

quick estuary
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youll learn it

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once you are taught

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or just use angle addition if you know

vital latch
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i do not know but would like to know ;D are there any videos online for this?

quick estuary
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idk

astral shadow
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Khan academy.

quick estuary
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and then expand cos2x

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1-2sin^2x

vital latch
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yeah that one i know

quick estuary
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you get a cubic in sin x

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using sin x as y

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3y-4y^3+2y^2-1=0

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you solve this

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and use the solutions lying strictly between -1 and 1

vital latch
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legit have no idea how to solve that with the 1 being there imma be honest with you

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otherwise i could probably factor out the y

quick estuary
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its a normal cubic equation

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4y^3-2y^2-3y+1=0

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and if u dont get rational roots

vital latch
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like the only way i know to solve those is long division

quick estuary
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then solution doesnt exist

vital latch
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but there's no denominator(?)

quick estuary
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for a cubic you hit and trial a bt

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bit

vital latch
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yeah i think thats what my uni teacher said to

quick estuary
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like look here

vital latch
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you just guess and hope for the best

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try 0 -1, 1, -2, 2

quick estuary
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whenever sum of coeeficients is 0

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x-1 is always a factor

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so you will get y=1

vital latch
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oh like -3x^3 + 3x^2 ?

quick estuary
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which will give a solution

vital latch
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-3 + 3 = 0?

quick estuary
#

ye

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factor theorem

vital latch
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got it

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thats a good one to know

quick estuary
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after one solution

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u divide make quadratic continue

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the usual

vital latch
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okok that checks out

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but if i were to get sin(3x) = cos(2x) tomorrow on my amazing test that i don't feel prepared for

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and i will check out angle addition but like yeah

quick estuary
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you wont

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if sin 3x expansion

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hasnt been taught yet

vital latch
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do you think they'd hang me alive if i do sin(3x) = sin(pi/2 - 2x)

quick estuary
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idk i have literally never used that method

vital latch
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i mean its university level and we're probably expected to know this, issue is i didnt do math for 5 years and remember 0

quick estuary
#

for trig eqns

vital latch
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well lets see if it works ,D

quick estuary
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this is in class 11

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for me

vital latch
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then we'd have 5x = pi/2

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x = pi/10

quick estuary
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which is one solution

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from the cubic youll get

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root 5 -1/4 as a root

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which is sin 18

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18 degree

vital latch
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yeah the same

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cause pi/10 is 18

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and then i think i can say

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  • 2 pi n
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and also do 2/5 pi n

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to get the other solutions

quick estuary
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adding 2pi/n doesnt give all solutions tho

vital latch
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better than 0 XD

quick estuary
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nevermind

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no

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from cubic youll get a root 5 +1/4 aswell

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2pi/5 yes

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youll also get pi/2

vital latch
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wouldn't we get pi/10 + 2pi/5 -> 5pi/10 which is pi/2

quick estuary
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as a solution

vital latch
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hmm

quick estuary
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pi/2 coming from the fact that the root of the cubic was 1 aswell

vital latch
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ok so what solution am i missing?

quick estuary
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cubic will guarantee you all answers

vital latch
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i have pi/10, pi/2

quick estuary
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2pi/5

vital latch
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ok so we set n to 2

quick estuary
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n?

vital latch
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pi/10 + 4pi/5 = pi/10 +8pi/10, = 9pi/10

quick estuary
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2npi/5 isnt correct

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2pi/5 is one solution

vital latch
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yes but when n is = 1 you get that

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i think

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wait

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look

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pi/10 + 2pin/5

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when n is 0

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we get pi/10

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when n is 1

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we get pi/2

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when n is 2

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we get 9pi/10

quick estuary
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9pi/10 hm

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cos 18pi/10

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sin 27pi/10

vital latch
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which is uhh.. 162 degrees?

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but sin(18) = sin(162)

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i think

quick estuary
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cos 18pi/10 is 4th quadrant

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cos pi/5 youre getting from this

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sin 27pi/10 gives you

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cos 7pi/10

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sin*

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cos 3pi/10

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definately not equal

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cos 3pi/10 and cos 2pi/10

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using cos (-x) = cos x and sin (pi-x) =sin x

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oh wait

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sin 3pi/10

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ok youre right

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its is 2/5n

vital latch
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IT DOES WORK!?

quick estuary
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ye

vital latch
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holy macaroni

quick estuary
#

had to check

vital latch
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ok that's good news

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i will still try to learn angle addition because i want to use the "good" techniques

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but while im trying to learn this one is a little easier :p

quick estuary
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for trig equations factoring is the best methof

vital latch
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yeah it does seem to be very good

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do you have any recommendations for good geometry problem videos?

quick estuary
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my own gemetry is ๐Ÿ’€

vital latch
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because we're expected to know all these formulas but when i tried to look online for like precalc / calculus geometry it's really lackluster compared to the problems in the last exams..

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like this one

quick estuary
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these are 11th grade problems

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can translate?

vital latch
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im not entirely sure what the idea is here

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a chord in the unitcircle is seen from a point on the circle with the degree of 120, (see figure), decide the chords length

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so there is the "randvinkelsats"

quick estuary
#

thats doable

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you just

vital latch
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Inscribed angle

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?

quick estuary
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make the centre

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youll get angle in centre

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and use sine law

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and done

vital latch
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wait so what i did

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is this

quick estuary
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oh bruh

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this is straight observation

vital latch
quick estuary
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answer is 1

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you find the wrong angle

vital latch
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is this correct?

quick estuary
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that too incorrect

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๐Ÿ’€

vital latch
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that's what i was afraid of

quick estuary
#

look

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both those are radii

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and

vital latch
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my lines u mean?

quick estuary
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its a cyclic quadrilateral isnt it

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ye

vital latch
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yes they are 1

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uhh

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quadrilateral

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lemme google rq

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ah

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well yes it is

quick estuary
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then by its property

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a cyclic quads opposite angles

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are supplementary

vital latch
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but are there rules that the opposite corner in a quadrilateral always is opposite angle?

quick estuary
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so middle angle 60

vital latch
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oh

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supplementary

quick estuary
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and radii are 1

vital latch
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got it

quick estuary
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so its equilateral

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wait

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i have commited error

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my bad

vital latch
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no problem dear sir

quick estuary
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your angle is correct

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thats not a cyclic quad

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all 4 points have to touch circle

vital latch
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so can i use the inscribed angle?

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but i think they do

quick estuary
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so what you do is you join it to the top

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yes b=2x is correct

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then you apply sine rule

vital latch
#

cos no?

quick estuary
#

cos?

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use sine for this

vital latch
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c^2 = 1+1 -211 cos(120)

quick estuary
#

so complex la

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use sine rule

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much easier

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sin 120 /x = sin 30

vital latch
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c^2 = cos(120) which is sqrt1/2?

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or?

quick estuary
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you get imaginary

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how

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wait

vital latch
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ah wait

quick estuary
#

its 1+1

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2(1-cos 120

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use sine law

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search it up

quick estuary
vital latch
#

its the a/sin A = b/sin B = c/sinC right?

quick estuary
#

ye

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2 x 3/2

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is c^2

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c is root 3

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sdone

vital latch
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and how would you apply it here then? say that 1/sin(30) = x/sin(120)

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uhh

quick estuary
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just plug values

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sin 120/sin 30 =x

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sin 120 is cos 30

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cot 30 =x

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x is root 3

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same answer

vital latch
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ohh ok

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i think i see

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wait is sin120 cos30?

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๐Ÿค”

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oh yeah

quick estuary
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yes

vital latch
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or no

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wait wat

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isnt sin(60) = cos(30)

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uhhh

quick estuary
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and?

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you know the graph of sine?

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sin90+x is cos x

vital latch
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i know it's a bit further ahead

quick estuary
vital latch
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isnt sin90-x also cos x?

quick estuary
#

from this

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yes

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why cant both be true

vital latch
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it just feels wrong

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but ok

quick estuary
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once u see the graph

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it will clear out

vital latch
#

ok but then i think i understand this one

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as long as the point in the middle connects to the same lines as the other angle it's gonna be double?

quick estuary
#

wut?

vital latch
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like to get the angle

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using the inscribed angle theorem

quick estuary
#

thats a theorem?

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lol

vital latch
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im not sure how you get it otherwise

quick estuary
#

oh this

vital latch
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but im having issues seeing how it works with this problem..

quick estuary
#

angle at centre is double angle inscribed

quick estuary
vital latch
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ok awesome

quick estuary
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you just find the other angle using this

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360-240

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then sine/cosine rule

vital latch
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okok

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and how would you approach this one for example?

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translation on its way

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20 meters of steel wire must be used to enclose a flowerbed in the form of
a sector of a circle with an angle ฮฑ between 0 and ฯ€ and radius r (see figure). For
which radius of the circle sector is the area of the discount the largest, and what is it
maximum area?

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i assume we want to set up a function right?

quick estuary
#

area of discoiunt?

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oh got it

vital latch
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uhh

quick estuary
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so

vital latch
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is the area of the flowerbed the largest

quick estuary
#

yeah got it

vital latch
#

rabatt means flowerbed and discount XD

quick estuary
#

2pir * theta

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is circumference

vital latch
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yeah so 2pir is circumferenece

quick estuary
#

+2r

quick estuary
vital latch
#

yep

quick estuary
#

for a sector you multiply theta in radians

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that +2r is 20

vital latch
#

ohhh ok

quick estuary
#

write that down kek

vital latch
#

i think i can remember it

quick estuary
#

2r(1+pitheta)

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=20

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r(1+pitheta)=10

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you have to maximize

vital latch
#

ok so normally entire circumference is 2pi*r

quick estuary
#

yep

vital latch
#

and then in this scenario when its a circle sector we have

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2pi*r * theta

quick estuary
#

yes

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you underdtood why the theta multiplied?

vital latch
#

and you set that equals to 20 for the length of the steel wire?

quick estuary
#

then yes

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because thats how much wire we have

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now

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r+ rpitheta=10

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r pi theta = 10-r

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theta = 10-r /rpi

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okay?

vital latch
#

and wait wait you say r twice because of the radius apart from the circlesector right

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just making sure im with you

quick estuary
#

yes

vital latch
#

liek this

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yeah

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ok

quick estuary
#

yed

vital latch
#

im with you then

quick estuary
#

k?

vital latch
#

yes

quick estuary
#

now

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area is pir^2

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of whole circle

vital latch
#

yep

quick estuary
#

so for sector

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pi r^2 theta

vital latch
#

so then we get

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pi r^2 * (10-r/rpi)

quick estuary
quick estuary
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so it cancels

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pi and r

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r(10-r)

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when is this maximum?

vital latch
#

low r

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?

quick estuary
#

if u know a little bit of quadratic eq

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no

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10r-r^2

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u know differentiation?

vital latch
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i probably do but i do not know that word

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derivative?

quick estuary
#

derivative

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minima

vital latch
#

yeye

quick estuary
#

yes

vital latch
#

so this would be

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10 - 2r

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right?

quick estuary
#

yes

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u know when maxima or minima occurs?

vital latch
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when you factor and its equal to 0?

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i think?

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thats the turning point?

quick estuary
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uhh

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close

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when dy/dx is 0

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so 10-2r=0

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r = 5

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put this r

quick estuary
vital latch
#

ohh alright

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and then get 25?

quick estuary
#

you get 25

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yes

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you can find this maxima in many many ways

vital latch
#

ok then i think im with you all the way

quick estuary
#

using AM GM inequality

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using quadratic

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but its okay

vital latch
#

am gm inequality, another term i've never heard of ;D

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thank you so much for all of this help btw

quick estuary
#

np

#

its just practice for me

vital latch
#

did you have any recommendation for videos that target these kind of geometry problems?

quick estuary
#

i dont study from videos kek

vital latch
#

XD

quick estuary
#

books>

vital latch
#

like the issue with my uni books is that the problems dont have the steps to the solution, just the answers

quick estuary
#

all this was in my school curriculum kek

#

uni for me means different kek

#

uni is after college

#

these problems are my grade 10

vital latch
#

ah yeah this is probably college for you

quick estuary
#

no lmfao

vital latch
#

like 19 year olds?

quick estuary
#

these are elementary

#

no

#

15

vital latch
#

XD

#

i mean we did have this back then too

#

its just that we're supposed to still know it

quick estuary
#

bro frogor

vital latch
#

big time

#

5 years without math

#

it all went straight out of the head

quick estuary
#

lo

vital latch
#

literally was wondering what happened when i multiply negative values

#

i was 90% sure it was gonna be positive

quick estuary
#

๐Ÿ’€

vital latch
#

but now i have to continue as if i were just in grade 11 or w/e u said it was

quick estuary
#

ye

vital latch
#

ok if you want more practice that would help me enormeously with the understanding

quick estuary
#

๐Ÿ’€

#

probably dm now

vital latch
#

oh yes

#

.close

vocal sleetBOT
#
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vocal sleetBOT
#
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long flame
#

finding gradient using limit method of $ y = \frac{1}{x^2}, x = 2$

long flame
#

$ y = \frac{1}{x^2}, x = 2$

twin meteorBOT
#

chlamydia

grizzled halo
#

any progress?

long flame
#

it's a bit messy but wait

#

w' rotate

twin meteorBOT
long flame
#

the problem is that what I call D, the y of x delta minus y of x, gives a fraction

#

so D / dx is complicated and i get lost trying to get to the answer which should be -2

#

i can however tell the pattern that when we expand y of delta x, and subtract y of x, we have the coefficient of delta x being -2. This coefficient is always also the final answer

#

but for the previous exercises i was able to get to the final equation through algebra and then plotting limit of dx -> 0 to get the answer but for this exercise I wasn't able to

#

basically we have $\frac{\frac{-2dx - dx^2}{1+2dx+dx^2}}{dx}$

twin meteorBOT
long flame
#

how can we solve this to become -2

#

(after having dx = 0)

magic surge
#

(-dx(2+dx)/(1+dx)^2)/dx = -(2+dx)/(1+dx)^2 = -2/1

#

algebra

#

what's gradient

long flame
#

slope

magic surge
#

isn't it like

#

3d

#

oh ok

#

ah slope

vocal sleetBOT
#

@long flame Has your question been resolved?

#
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โ€ข Type the command .close to free the channel when you're done.
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languid venture
vocal sleetBOT
languid venture
#

How can you solve an arg like that?

vocal sleetBOT
#

@languid venture Has your question been resolved?

languid venture
#

<@&286206848099549185>

languid venture
#

I dont understand what that even means

#

Usually i calculate arg of a and b

cursive turret
languid venture
#

Not just Z

cursive turret
#

arg(ab)=arg(a)+arg(b), so arg(izยฒ)=arg(i)+2arg(z)

#

i is just a complex number.

languid venture
#

Ahh ok I try

languid venture
cursive turret
#

what should be? its just an equation. 1 = arg(i)+2arg(z). solve it.

languid venture
#

Rught ok I try

vocal sleetBOT
#

@languid venture Has your question been resolved?

languid venture
cursive turret
#

the point is: you posted just a small part of the exercise, so it is nearly impossible to help you. What is asked in your example?

languid venture
cursive turret
#

you know the left side, you should know arg(i) so you should be able to calc arg(z).

languid venture
cursive turret
#

yes, so you can calc arg(z), but you still havent said what the goal of the example is.

languid venture
languid venture
#

Not full line

#

It also says there are many solutions?

vocal sleetBOT
#

@languid venture Has your question been resolved?

languid venture
#

<@&286206848099549185>

manic lava
#

Yeah?

languid venture
#

It asks if the solutions to that arg are a line a circle a not full line

manic lava
#

Lemme check

#

Should be a circle I think

languid venture
#

Why?

manic lava
#

Which book is it from?

languid venture
#

Its a old exam not book

languid venture
manic lava
#

Ok wait I'm thinking

#

U have the question pic somewhere?

languid venture
#

Yeah but italian

manic lava
#

No worries send

#

I'll try to solve it

languid venture
#

Question 2

manic lava
#

Yeah I'm thinking

languid venture
manic lava
#

??

languid venture
manic lava
#

Not yet

#

Explain no

languid venture
vocal sleetBOT
#

@languid venture Has your question been resolved?

vocal sleetBOT
#
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formal gazelle
#

So if we are converting the parent function $\frac{6}{x-3} + 5$ to the child function $\frac{6}{-3x-3} +5$ . IS THIS reflection over the y axis or the x axis. And is it a vertical dilation of 3? Or is it a horizontal dilation by a factor of 1/3? Or is it horizontaly dilated by 3?

twin meteorBOT
formal gazelle
#

<@&286206848099549185>

#

Had posted this an hour ago

#

in a diff channel

#

<@&286206848099549185>

dapper jay
#

they have the same y-intercept

#

both expressions

formal gazelle
#

That doesmt say anything useful?

dapper jay
#

it does

#

you can use that information to determine what axis its reflected over

dapper jay
#

think about it

vocal sleetBOT
#

@formal gazelle Has your question been resolved?

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#
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formal gazelle
#

.reopen

vocal sleetBOT
#

โœ…

formal gazelle
#

Idk hoiw

vocal sleetBOT
#

@formal gazelle Has your question been resolved?

formal gazelle
#

<@&286206848099549185>

#

Kinda getting annoying

hollow thunder
#

so basically for this question if you cant rememeber it, I try to roughly sketch it

formal gazelle
#

Its kinda hard to sketch this ngl

hollow thunder
#

I would just plug in points

formal gazelle
#

still its kinda confusing

#

I dont get it

hollow thunder
#

hmm ok so the parent function x is a -3x in the child function so y-value when x is -1/3 would be the same as y value when x is 1 in the parent so if any arbitrary point on the parent were like (x,y) then a point on the child would be (-x/3,y)

#

so then you can see how it changes from the (-x/3, y)

#

does that kinda make sense?

formal gazelle
#

no?

hollow thunder
#

wait a sec lemme see if I can find something

#

basically use that

#

does that help?

#

if not I can help break it down

#

look at your parent function as f(x)

#

how would you represent you child function in terms of f(x)??

vocal sleetBOT
#

@formal gazelle Has your question been resolved?

vocal sleetBOT
#
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daring sinew
#

How can one calculate trigonometry functions without a calculator?

hushed pewter
#

But it depends on the function and input

final bridge
#

what question is it?

daring sinew
#

Lets say for an example cos 800ยฐ = 800-360*2 = 800-720 = cos 80ยฐ

#

so cos 80ยฐ without a calculator

final bridge
#

damn

daring sinew
#

.close

vocal sleetBOT
#
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grand void
#

I'm not sure how to define x in terms of theta, can anyone offer any insight?

late ingot
#

$\cos^{2}\theta+\sin^{2}\theta=1$

twin meteorBOT
#

b0ngl0rd

late ingot
#

that has a radius of 1

#

the integrand has a radius of 16

grand void
#

I factored out the 16.

late ingot
#

so you got the 1 - sin^2 as the identity, which works

#

you gotta find what you replace x with.

grand void
#

Not sure how to put x in terms of theta

late ingot
#

trig sub.

grand void
#

Somehow it's 4sin(theta)?

#

How was that calculated?

late ingot
#

x/4 = sin theta

#

x = 4 sin theta

grand void
#

Where did we know the value was going to be sin?

#

And that it was equal to x/4?

late ingot
#

look at your work

#

you'll see x/4 appears

#

but thats slightly confusing, thats why i was trying to show through the identity how to get it

#

$16\cos^{2}\theta+16\sin^{2}\theta=16$

twin meteorBOT
#

b0ngl0rd

late ingot
#

square root the whole thing

#

$\sqrt{16\left(\cos^{2}\theta+\sin^{2}\theta\right)}=\sqrt{16}$

twin meteorBOT
#

b0ngl0rd

late ingot
#

$4\sqrt{\cos^{2}\theta+\sin^{2}\theta}=4$

twin meteorBOT
#

b0ngl0rd

late ingot
#

that constant is the multiple you need for the substitution

#

$\sqrt{r^{2}-\left(r\sin\theta\right)^{2}}$

grand void
#

I do see x/4, how do we know that was equal to sin? (thank you for showing me this other clever trick as well).

late ingot
#

because the identity matched the form, all that we needed to do was scale the identity by the radius of the semicircle we are working with

#

sqrt(16) = 4 = radius

twin meteorBOT
#

b0ngl0rd

grand void
late ingot
#

no. the reason is exactly what your work shows, that the radius scales x, specifically by a factor of 4

#

thats why we take x/4 = sin theta

#

then to get x we multiply

grand void
# late ingot

So basically x is always going to be a*sin(theta)?

late ingot
#

no

#

it depends on the identity

grand void
#

These.

#

Okay gotcha

late ingot
vocal sleetBOT
#

@grand void Has your question been resolved?

grand void
late ingot
#

if you know the substitution you should be able to do it from the beginning with no work done.

vocal sleetBOT
#

@grand void Has your question been resolved?

vocal sleetBOT
#
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โ€ข After 15 minutes, feel free to ping <@&286206848099549185>.
โ€ข Type the command .close to free the channel when you're done.
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junior adder
#

Need help with combinatorics

vocal sleetBOT
junior adder
#

Is there a formula to find how many different variations of two dice equaling a certain number

#

say I want to find how many ways I can roll two dice to equal the number 7

#

is there a formula for that?

regal bane
#

There's a method called "stars and bars", which can solve it, and some problems like it

junior adder
#

could i use lets say 6 choose 2?

#

or something like that

regal bane
#

What's your thought process?

junior adder
#

welll

#

to determine the total amount of combinations two dice have

#

i did 6 *6

regal bane
#

But I thought you wanted the number of ways to roll a 7

junior adder
#

yea

#

im hitting a road block

#

I havnt learned stars and bars yet

regal bane
#

In this case, it's also pretty easy to count all of the cases

#

1+6,2+5,3+4,4+3,5+2,6+1

junior adder
#

yea but

#

using math would be cooler

regal bane
#

Sure. So to connect this to a more common problem:
You want the number of positive integer solutions to the equation x + y = 7

junior adder
#

right

#

x being dice 1 and y being dice 2

#

if x 1 is = 1 then y has to be 6

regal bane
#

Let's say I take 7 stars and 1 bar, and put them in a row like this:
***|****

#

That permutation of stars and bars corresponds to the solution 3 + 4 = 7

#

So every arrangement of stars and bars corresponds to a solution to the equation

#

The question is NOW:
How many ways can I arrange 7 stars and 1 bar?

junior adder
#

5 ways?

#

wait

#

6

regal bane
#

Oh wait I am making a mistake. 0s are allowed in the solution, when using this method

#

|*******

#

Is 0 + 7 = 7

junior adder
#

thats impossible

regal bane
#

But obviously that can't happen with dice

junior adder
#

I was given this from the lecture

#

bayes rule

regal bane
#

This seems to be a pretty different question

vocal sleetBOT
#

@junior adder Has your question been resolved?

vocal sleetBOT
#
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โ€ข After 15 minutes, feel free to ping <@&286206848099549185>.
โ€ข Type the command .close to free the channel when you're done.
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Read #โ“how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

faint matrix
#

Hey can i get help for a linear algebra question?

hollow thunder
#

sure I can try to help

faint matrix
#

so i can send you my work

#

but warning its a whole page long

#

but please tell me if i was on the right track

#

and these are the answers for this question:

hollow thunder
#

ok

faint matrix
#

this is my work

#

but i checked and im pretty sure my answer doesnt line up with the answer given in the answer key

#

and i sent the answers above

hollow thunder
#

Right so you just want to change it into I think it's called identity matrix

faint matrix
#

yes thats what I thought shoulvde been done in this question

#

I wrote it in terms of a augmented matrix or you could say identity matrix

hollow thunder
#

is the bottom one the final matrix?

faint matrix
#

yes

#

but im not sure if its right

hollow thunder
#

you want to make the ones at the top also 0

faint matrix
#

thats why I need help from someone who could help solve this questionb

hollow thunder
#

so you can get top row 1 0 0 0

#

next 0 1 0 0

#

and so on

#

the matrix is basically a system of equations

faint matrix
#

but i dont know how I could do that

#

it seems too complicated to get the top row 1 0 0 0

#

is it possible if you could show me the proper steps to solve this system of equations?

#

then I could compare it with my work?

hollow thunder
#

you have to work you down from the first row make the numbers under the first ones all zeros

faint matrix
#

I did that

#

until i got all the way down to 823/105

hollow thunder
#

you want to make it one so it's easier to cancel out the ones below

faint matrix
#

one more thing I think I could do here is turn that 823/105 in to a 1 and i know how to do that

hollow thunder
#

yes exactly

faint matrix
#

could you show me the steps?

faint matrix
hollow thunder
#

so divide the first row until first is 1

drifting jackal
hollow thunder
#

that too

faint matrix
#

Yes thats one thing

drifting jackal
#

Like you wrote in 60/90, that equals 2/3

#

Makes the math a tad easier

faint matrix
#

ah yes

#

I tried to do that sometimes

#

but then i stopped simpliyfying

#

overall do all my steps seem correct?

#

cuz if they do Im pretty sure my final answer will still be wrong.

hollow thunder
#

try to get the diagonal ones to 1 and all the others below that to 0

faint matrix
#

bro

hollow thunder
#

then you have to get all the ones above it to 0 too

faint matrix
#

thats too difficult i feel

#

i have no idea how

drifting jackal
#

What's this number here?

faint matrix
#

1760/90

drifting jackal
faint matrix
#

but overall do you guys think my steps seem correct and on point?

#

and if not could someone maybe try this question and show me their steps?

hollow thunder
#

you need to finish but other than that I think so

faint matrix
#

id really appreciate it

hollow thunder
#

I can't really show you rn but I can walk you through it step by step

faint matrix
#

on call?

#

like can i screen share

hollow thunder
#

like can you take a picture of where your final matrix is now?

faint matrix
#

yes one sec

#

doing that right now

hollow thunder
#

first step is to simplify the fractions

faint matrix
#

i got an insane number

#

final matrix is bottom right

hollow thunder
#

can that be simplfied?

drifting jackal
hollow thunder
#

I think it would be best if you simplified before going forward

#

right

#

so that way the numbers are easier to work with

faint matrix
hollow thunder
#

so that could be simplified

faint matrix
#

i cant go back and simplify tho now

drifting jackal
faint matrix
#

shit

#

could you explain how

hollow thunder
#

It might be a calculation error

drifting jackal
faint matrix
#

or let me check

drifting jackal
#

,calc 2 * (625/90) - 5

twin meteorBOT
#

Result:

8.8888888888889
drifting jackal
#

,calc 2800/90

twin meteorBOT
#

Result:

31.111111111111
faint matrix
#

fuck

#

fuck

#

i give up

hollow thunder
#

chill

faint matrix
#

yea your right

#

my bad

#

i cant

#

ive been working on this for 20 mins

#

or 15

#

or even 30

#

i made a calculation error

hollow thunder
#

it fine I make them all the time

faint matrix
#

i know but i have a midterm on this tmmrw

hollow thunder
#

try simplifying the fractions to make calculating easier

faint matrix
#

thanks your right

drifting jackal
faint matrix
#

yea hundred percent

#

i shouldve simplified right away

hollow thunder
#

yeah

faint matrix
#

but anyway i gotta ask

#

if on a midterm

#

or sorry

hollow thunder
#

if worst comes to worst just write out a system of equations

faint matrix
#

if i was trying to row reduce, could i still find the values of each vairable with a matrix that looks like this

hollow thunder
#

thats basically all it is

faint matrix
hollow thunder
#

wdym

faint matrix
#

so this is the final matrix i got

#

but with using the info in this final matrix

#

can i still derive the values of x,y,z,w

hollow thunder
#

not if they are calculated incorrectly

drifting jackal
faint matrix
#

so is it not possible to derive the values of x,y,z,w if I did the algebra wrong?

hollow thunder
#

you can think of it like 0x+0y+0z+1w=(number)

faint matrix
#

shouldnt i still be able to derive the values

#

even if it gives me the wrong answers?

hollow thunder
#

the matrix is sorta just a system of equations

faint matrix
#

like if i use subsitition method i could get the values of x,y,z,w

#

no?

drifting jackal
faint matrix
drifting jackal
#

You'll get a set of values for x, y, z, w but it wouldn't be correct

faint matrix
#

ok thanks

#

thats what i wanted to know

hollow thunder
#

unless your teacher specifically asks for using the matrix I would just use a system of equations

faint matrix
#

Because I was just confused as to whether or not a system of equations has to be in rref in order for you to derive the values of varaibles

faint matrix
hollow thunder
#

exactly

#

thats really all the matrix is

faint matrix
#

cuz yea im def gonna do that

hollow thunder
#

substitution and elimination

faint matrix
#

but he most likely will ask us about ref and rref

hollow thunder
#

well if you think about it like the first row is 90x+90y+80z+12w=124 (im making up numbers) and the other rows like that and your just solving it in a different way

faint matrix
#

yea that makes sense

hollow thunder
#

you can think of it like a fancy way of writing it

faint matrix
#

ref and rref is the cancer way to solving for variables i feel like

hollow thunder
#

it's different

drifting jackal
faint matrix
#

gaussian elimination?

#

isnt that what we use for ref and rref?

hollow thunder
#

what your doing basically

faint matrix
#

oh wtf

#

i didnt realize that for sum reason

hollow thunder
#

its just the row reduction things

faint matrix
#

also I have one more question I'd like solved before I go

#

if possible

hollow thunder
#

sure

faint matrix
#

this one will also be on my midterm tomorrow and it involves financial mathematics

hollow thunder
#

I can try but i might not know how to solve

faint matrix
#

Is there someone who might know financial mathematics?

#

but yea please try if you can

#

i need help with specifically b

#

and d

#

for this question all i know is that you can use annuity formulas or you can use sigma notation to solve this.

drifting jackal
# faint matrix oh wtf

Yeah with gaussian elim, you multiply some row then add/subtract it to another, same thing with general elimination because you would take one equation, multiply it by some value to then add/subtract with some other equation to eliminate variables. The matrix is just the value form of general elimination

hollow thunder
#

yeah imma be honest im in middle school idk how to solve financial mathematics

faint matrix
#

ur in middle school and u know how to do ref and rref?

hollow thunder
#

uh yeah