#help-10

1 messages ยท Page 525 of 1

drowsy girder
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I see you can factor first equation

fallen mantle
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what do you get?

gritty dragon
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yeah I tried but I just didint get it

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Can maybe some help me like step for step

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<@&286206848099549185> can someone help me it due tomorrow and i don't want to get in any trouble

obtuse pebbleBOT
#

@gritty dragon Has your question been resolved?

gritty dragon
#

no

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it hasn't

trim oasis
#

So, one of the methods to solve this is to solve one of the equations for either x or y and then substitute the variables of the other equation with your result.

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I'd suggest solving 3y - 2x = 12 since it's the easier equation
Do you want to solve for x or for y?

gritty dragon
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yeah but i don't know hoe

trim oasis
#

I'll help you, don't worry
Let's solve for x, it doesn't really matter too much

gritty dragon
#

oke

trim oasis
#

So you want to solve 3y - 2x = 12 for x, do you know how to do that?

gritty dragon
#

I think you have to trace out the x

trim oasis
#

Yep, so you'll want to move everything that isn't x to the other side of the equation (i.e. a variable, a number)

gritty dragon
#

okay

trim oasis
#

So what you want to do is subtract 3y from both sides, does that make sense?

gritty dragon
#

so that is 2x=-3y+12

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yes

trim oasis
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Yep ๐Ÿ‘

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Well, almost actually

gritty dragon
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oh

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okay

trim oasis
#

It's
-2x = -3y + 12

gritty dragon
#

oh yeah

trim oasis
#

Don't worry about that, it's an easy mistake to make
So now, you want the -2 to be gone as well. This means you have to divide both sides by -2

gritty dragon
#

yes i understand

trim oasis
#

And then, the equation is...?

gritty dragon
#

x= 1,5-6

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1,5y

trim oasis
#

Exactly!

gritty dragon
#

oke

trim oasis
#

And now, you enter 1.5y - 6 for every x that appears in the other equation

gritty dragon
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oh isee

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yes

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so now we got to do that for the y aswel

trim oasis
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Then, the equation becomes ${(1.5y - 6)}^2+4y^2-8y+2*(1.5y-6)$
And the good thing about this is that you only have y's and no x's

warm shaleBOT
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Asgard

trim oasis
gritty dragon
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oh

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wait let me see

trim oasis
#

For now, just try to get everything with a y or a y^2 on one side, you're going to bump into a problem you can't solve with eihgth grade maths

gritty dragon
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okay so I can't answer that main question of 5x+5y

trim oasis
#

The problem is that you have to solve a quadratic equation and that's not possible without guessing (at least at the moment, you'll learn a formula for it later)

gritty dragon
#

you mean a^2+bx+c

trim oasis
#

Oh, do you know that already? :D

gritty dragon
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yeah

trim oasis
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Fantastic, then you can solve it

gritty dragon
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GRADE

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NICE

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sorry caps

trim oasis
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Dw :>

gritty dragon
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so i am calculating the first question right now

trim oasis
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Mhm
Do you know how to solve the equation?

gritty dragon
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i am trying but if you could help me that would be great

trim oasis
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Alright :D

gritty dragon
#

thx ๐Ÿ™‚

trim oasis
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So first, let's try to make the (1.5y - 6)^2 easier
Just multiply (1.5y - 6)*(1.5y - 6)

gritty dragon
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so 1,5y*1,5y

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is 2,25y^2

trim oasis
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Not quite

gritty dragon
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oh

trim oasis
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When squaring this sort of expression, you have to sort of multiply everything with everything

gritty dragon
#

alr and how do we do that

trim oasis
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Like this

gritty dragon
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oh but I thought I was doing that

trim oasis
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So the result is a*a + a*b + a*b + b*b

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$a^2 + 2*ab + b^2$

warm shaleBOT
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Asgard

trim oasis
gritty dragon
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oh yeah I see

trim oasis
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That means our result is
$(1.5y)^2 + 3y*(-6) + (-6)^2$

gritty dragon
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yeah okay

trim oasis
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Not 21.5 lmao
Sorry, the bot seemed to skip the asterisk

warm shaleBOT
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Asgard

gritty dragon
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oh np

trim oasis
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Do you think you can solve this yourself?

gritty dragon
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yeah I am going to try

trim oasis
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Alright, tell me if you're stuck

gritty dragon
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i will

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I got -15,75y+36

trim oasis
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You seem to have dropped a y^2 somewhere ๐Ÿค”

gritty dragon
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oh

trim oasis
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The 36 is correct, but it's -18y, not -15.75y

gritty dragon
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oh

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I at first had 2,25y-18y+36

trim oasis
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Okay, well the correct result is 2.25 y^2 - 18y + 36

trim oasis
gritty dragon
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yeah I think so

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so what do we do with this answer

trim oasis
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Alright, so now we're at 2.25y^2 - 18y + 36 + 4y^2 - 8y + 2*(1.5y - 6)

gritty dragon
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yes

trim oasis
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We just have to simplify one more thing

gritty dragon
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the 4y^2-8y+2*(1,5y-6) right

trim oasis
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Exactly
And we'll make our lives a whole lot easier if we solve 2*(1.5y - 6) first

gritty dragon
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yeah so that is 3y-12

trim oasis
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Yep

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So now, it's
2.25y^2 - 18y + 36 + 4y^2 - 8y + 3y -12

gritty dragon
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yes

trim oasis
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And we can add things like 2.25y^2 and 4y^2 together to simplify everything even further

gritty dragon
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yes so we get 6,25y^2-26y+24

trim oasis
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Exactly!

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And the equation that we get is
6,25y^2-26y+24 = 3, but we need the 3 to be a zero, so just subtract three on both sides

gritty dragon
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oke

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so 6,25y^2-26y+21

trim oasis
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๐Ÿ‘

gritty dragon
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nice

trim oasis
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Now, just enter the values into the formula for quadratic equations

gritty dragon
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oke

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don't we need to divide everything by 6,25 firs

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first*

trim oasis
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Not really

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Just enter
6.25 for a
-26 for b
21 for c

gritty dragon
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oh thanks

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I am stuck man

trim oasis
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Where exactly?

gritty dragon
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My calculator says math error

trim oasis
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Could you send what you entered?

gritty dragon
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-26+ -26-4**-26* *21

trim oasis
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So you entered +-?

gritty dragon
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No only the +

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and then afterward I would do the same but then for -

trim oasis
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Mhm okay

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Could you put parentheses around the (-26) and try again?

gritty dragon
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i will try

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yeah that worked

trim oasis
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Awesome :D
What's the result?

gritty dragon
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-2190.625

trim oasis
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Hmmmm

gritty dragon
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wait

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i did something wrong

trim oasis
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I think so...

gritty dragon
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-1640,625

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I still think its wrong

trim oasis
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Give me a second

gritty dragon
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and the other answer was -1803.125

trim oasis
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The two blue points are the ones we're looking for
They're pretty close to 1 and 3

gritty dragon
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oh then I was def. wrong

trim oasis
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The solutions of 6,25y^2-26y+21 = 0 are
y_1 = 1.09
y_2 = 3.06

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Oh wait hold up

gritty dragon
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alr I will wait

trim oasis
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There are two solutions, because it's a quadratic equation, but we need one value for y so we can continue to work with it

gritty dragon
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so we have to go back to 3y-2x=12

trim oasis
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I don't think we made a mistake there, the problem is somewhere else

gritty dragon
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oh but if we want to know the value of y we have to trace back the y

trim oasis
#

Oh wait
Let's try both y for what we're going to do and see if one matches and the other one doesn't
Then we can rule it out

gritty dragon
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smart idea

trim oasis
gritty dragon
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yesh I get it

trim oasis
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Awesome!

gritty dragon
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so 3y-2x=1.09 and 3y-2x=3,06

trim oasis
#

Not really, you have to substitute the y in there with the value, not the 12

gritty dragon
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so how would you write that down

trim oasis
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3*1.09-2x=12
and
3*3.06-2x=12

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Fricken Discord xD

gritty dragon
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hah

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3,27-2x=12

trim oasis
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Actually, we can do it even simpler

gritty dragon
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oe I like simple things

trim oasis
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Just use the equation we got before:
x = 1.5y - 6

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So
x_1 = 1.5*1.09 - 6
x_2 = 1.5*3.06 - 6

wait

gritty dragon
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what is wrong

trim oasis
gritty dragon
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what do you mean

trim oasis
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The question was 5x + 5y = ?

gritty dragon
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yas

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yes

trim oasis
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And since we have two y and we will have two x, there will be two values for "?"

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There will be
?_1 = -16.375
?_2 = 22.35

Hmmmm

gritty dragon
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we only have x and y what could it be

trim oasis
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Well, we have two y, that means we can calculate two x, which will result in two equations

gritty dragon
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2 coordination

trim oasis
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(I) 5*x_1 + 5*y_1 = ?_1
(II) 5*x_2 + 5*y_2 = ?_2

gritty dragon
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ahhh

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so we have the 2

trim oasis
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oooof I have no idea how to solve this tbh

gritty dragon
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oh its okay

trim oasis
#

Maybe another person can help you, try pinging the Helper role after 15 minutes
It's getting kind of late where I live unfortunately

gritty dragon
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yeah for me to

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its almost 11pm

trim oasis
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We're in the same timezone :D

gritty dragon
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where do you live then

trim oasis
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Germany ๐Ÿ‘€

gritty dragon
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i am from the netherlands

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found this on a site

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I don't know if its right i an just going to turn this in

trim oasis
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Nice :D
Well, good luck with your homework!

trim oasis
gritty dragon
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thx man you too

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I am to tired to go make math again so i am fine with it

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well asgard thx for your help

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.close

obtuse pebbleBOT
#
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timid silo
#

(sin20)(tan10+cot10) without a calculator

obtuse pebbleBOT
timid silo
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I just do not know how this is supposed to wkr

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work

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I converted into radians but this did not help my understanding

obtuse pebbleBOT
#

@timid silo Has your question been resolved?

#
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timid silo
#

.reopen

obtuse pebbleBOT
#

โœ…

timid silo
#

(sin20)(tan10+cot10) without a calculator

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<@&286206848099549185>

strong vale
#

easy

timid silo
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its easy I just forget how to do it

strong vale
#

2

timid silo
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yeah I know the answer

strong vale
#

what is sin(20) in terms of cos(10) and sin(10)

timid silo
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its just how to do it

strong vale
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do u know?

timid silo
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no

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i forgot how to do lots of trig

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its the identities i forgot

strong vale
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u know sin(2a) = 2sin(a)cos(a)

timid silo
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yes

strong vale
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ok apply it and solve problem

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u done?

timid silo
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i did something stupid I think

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(2sin10cos10)(sin10/cos10+cos10/sin10)

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is this a valid step?

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@strong vale

strong vale
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no this is fine

timid silo
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i dont know what to do next

strong vale
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now carry out the multiplication

timid silo
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I did it wrong

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and got 4

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after I add both terms

strong vale
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how u get 4

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(2sin10cos10)(sin10/cos10+cos10/sin10) start from here

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and walk me through what u did

timid silo
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no

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i just dont know what im doing tbh

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could you please walk me through the steps

strong vale
#

Wht is $2\sin{10}\cos{10} \times \frac{\sin{10}}{\cos{10}}$

warm shaleBOT
#

azeem321

strong vale
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no im not solving it for you

timid silo
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i dont want u to solve for me

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if i wanted an answer i just use my calculator

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this looks like sin10/2sin10 but its not

strong vale
#

carry out the multiplication and tell me your result

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what is $\frac{\cos{10}}{\cos{10}}$

warm shaleBOT
#

azeem321

timid silo
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1

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omg i am cumb

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dumb

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ok

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2sin^2(10)+2cos^2(10)

strong vale
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yes

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but it's fine keep studying and u will be less dumb soon

timid silo
#

we did this topic months ago

strong vale
#

yes

timid silo
#

and my teacher randomly gives this assignment in the middle of studying logs

strong vale
#

trigonometry will follow you for years in your math classes so get good at it

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when u get rusty watch youtube videos

timid silo
#

yes i do that sometimes

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i just need review

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ty โค๏ธ

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.close

obtuse pebbleBOT
#
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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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copper lantern
obtuse pebbleBOT
copper lantern
#

isnt this correct?

haughty coyote
#

,rotate 180

warm shaleBOT
haughty coyote
#

wtf

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what are these angles

copper lantern
#

sorry the pic is messed up

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lol

haughty coyote
#

lmao

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are you trying to integrate that fraction ?

copper lantern
#

you mean 0/x-3?

haughty coyote
#

no the rational fraction of "degree" 3/1

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Cause then I'd say the result looks good to me

copper lantern
#

im supposed to use polynomial division on those 2 expressions and then integrate that

haughty coyote
#

,w integrate (x^3-3xยฒ+2x-6)/(x-3)

warm shaleBOT
dreamy river
#

@timid silo

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Sup

copper lantern
haughty coyote
#

no

copper lantern
#

how is there a x^2+6

haughty coyote
#

expand it

copper lantern
#

ohh yeah ok

haughty coyote
#

idk why it chose to write it that way

copper lantern
#

but look

haughty coyote
#

why did you integrate ?

copper lantern
#

i thought we were supposed to lol

haughty coyote
#

don't see it written anywhere

copper lantern
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so do i just write x^2+2?

haughty coyote
#

what are you going to do if not try it

copper lantern
#

yeah you were right

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thanks

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can i ask u another question

haughty coyote
#

just post it

copper lantern
#

this is ibp tho

haughty coyote
#

yes

copper lantern
#

i've tried this multiple times and have gotten it wrong

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i would show you my work but its all messy

haughty coyote
#

differentiate y

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integrate e^-2y

copper lantern
haughty coyote
#

take the 9 out of the integral, don't bother with it

copper lantern
#

can i do this with tabular notation?

haughty coyote
#

what do you call tabular notation ?

copper lantern
#

u & dv

haughty coyote
#

if you want. I always forget how that looks but if that's what you're familiar with

copper lantern
#

ok i'll try

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so i differentiate y until it's 0 right?

haughty coyote
#

Apply the formula, stop doing IBPs when you think it's not the easiest step anymore

copper lantern
#

?

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oh yeah i put a negative in front of the 1

haughty coyote
haughty coyote
copper lantern
haughty coyote
#

depends on how you want to write the final result. I put in factored form, you can expand if you want

copper lantern
#

i got -1/2ye^-2y-1/4e^-2y

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but i haven't added the 9 in yet

haughty coyote
#

you'll notice it's the same

copper lantern
#

so do i put the 9 over the 2 & 4?

haughty coyote
#

you do whatever you want. There are many ways of writing this

haughty coyote
# copper lantern

software like that should accept all equivalent answers as correct

copper lantern
#

oh ok so then i have to do the bounds now

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that's the issue

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i got this answer before

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and it was incorrect

haughty coyote
#

looks wrong to me

copper lantern
#

its the same answer you got though

haughty coyote
#

you forgot to subtract the value at 0

copper lantern
#

oh yeahh thank you

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do you mind helping with this

haughty coyote
#

I'd expect terms of all degrees from 3 to 0

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not just 3

copper lantern
#

what do you mean?

haughty coyote
#

just integrate

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by parts

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then integrate by parts

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then integrate by parts

copper lantern
#

u = t^3?

haughty coyote
#

just differentiate t^3

copper lantern
#

ok ill do that

haughty coyote
#

it's not hard when you got a polynomial, you take it's derivative until there's no polynomial anymore

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guarantees the process ends

copper lantern
#

true i'll differentiate t^3 and integrate e^-2t

haughty coyote
#

,w integrate -8t^3 e^(-2t) dt

warm shaleBOT
copper lantern
#

oh yeah let me add the 8

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-8

haughty coyote
#

looks good to me

copper lantern
#

nvm i forgot the +c

haughty coyote
#

yes

copper lantern
#

mateo you are the literal goat

haughty coyote
#

I just told you to IBP and used wolfram calm down

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and checked your answers

copper lantern
#

loll yeah i know but i ask some other people and they just tell me idk what im doing and to completely relearn ibp

haughty coyote
#

You look decently at easy with it yeah

copper lantern
#

so when i get someone that doesnt call me stupid im like enlightened lolll

haughty coyote
#

could get some more practice as these are very easy IBPs that you shouldn't struggle with, but for a help channel that's exceeding expectations for sure

copper lantern
haughty coyote
#

If you can do the exercises and you understand the method, the only thing left to "learn" is experience

copper lantern
#

yeah you're right

haughty coyote
#

That's often the difference on these problems between the help-seeker and the help-giver: we've seen these problems before, we know how to solve them, sometimes in our heads, and we can use methods that we're familiar with that you're not, it allows us to do these things more easily

#

experience makes one hell of a difference

copper lantern
#

for sure i agree

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tbh i just like to make sure what the u & dv is for this because im not always sure

haughty coyote
#

It's like if you scroll up #help-6 with AuHasard, I had 4 methods for his limit

haughty coyote
copper lantern
#

i put u=lnx

haughty coyote
#

yes

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indeed

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first intuition as well

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reduces to a nice IBP

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you can do that one on your own I think

copper lantern
#

ill try

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i think that lnx only differentiates to 1/x

haughty coyote
#

I don't like the "I think" here

copper lantern
#

i mean i know that it does

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& it stops there or else it's too complicated

haughty coyote
#

Actually this one can also be done without u-sub

copper lantern
#

i got 1/3x^3lnx-1/3x^2

haughty coyote
#

,w integrate 8ln(x)/xยฒ

warm shaleBOT
haughty coyote
#

easy check

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think it went the full IBP way

copper lantern
#

yeah thats different from what i got then

haughty coyote
#

and clearly not by just a constant

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Fun fact: sometimes that constant difference is very hard to spot and 2 expressions are both correct even though they look significantly different

copper lantern
#

true

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but im not sure what i did wrong

#

i could have done 1/x(1/3)x^3 instead

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but x^3/x = x^2

obtuse pebbleBOT
#

@copper lantern Has your question been resolved?

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waxen musk
obtuse pebbleBOT
waxen musk
#

anyone out there?

warm pine
#

what class is tghius

#

*this

waxen musk
#

Cal 1

warm pine
#

pls find someone else sorry

waxen musk
#

no probs thanks for replying atleast @warm pine

#

@analog python

#

@zinc flax

obtuse pebbleBOT
#

@waxen musk Has your question been resolved?

obtuse pebbleBOT
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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.

serene hatch
obtuse pebbleBOT
serene hatch
#

I don't know how to approach this

#

<@&286206848099549185>

obtuse pebbleBOT
#

@serene hatch Has your question been resolved?

obtuse pebbleBOT
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daring sparrow
#

An integer is divisible by 11 if, and only if, the alternating sum of its digits is divisible by 11.

Does this prove both sides? or just the If n is divisible by 11 part?

obtuse pebbleBOT
#

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near burrow
#

any idea how to solve this

obtuse pebbleBOT
near burrow
#

q 3

#

,rotate

warm shaleBOT
fallen mantle
#

QPS + QRS = 180

near burrow
#

okay

#

so

#

b + d + c = 90

#

a = 60?

#

i need to know how to work it out

fallen mantle
#

b + d + c = 180
a + d = 180

#

d = 180 - a

near burrow
#

okay

fallen mantle
#

so: b + d + c = 180
b + (180 - a) + c = 90

near burrow
#

a + d = 180 because of angles on a line right

#

= 180

fallen mantle
#

do you rmb the angle inside a four sided is always 360?

#

since there is already 2 angles with 90, so a+d would be 360-90-90

near burrow
#

yeah

#

angles of a quad = 360

#

wait

#

oh

#

so a + d = 180

#

im so confused

#

i hate geometry xd

fallen mantle
#

since b + (180 - a) + c = 180

near burrow
#

is 180 - a = 30

#

since 3 x 30 = 90

fallen mantle
#

the 180 can be cancelled out each other

near burrow
#

so what would i write

#

to prove b + c = a

#

ill probably get it if i write it out

fallen mantle
#

b + d + c = 180
a + d = 180
d = 180 - a

b + (180 - a) + c = 180
b + c = 180-180+a
b+c = a

#

done

near burrow
#

i still dont get it wtf

#

get the first line

#

why does a + d = 180

#

angles on a line or?

#

it cant be coint <'s because we arent using paralell lines

fallen mantle
#

rmb that all the 4 angles in a 4 sided polygon is always 360
since there is already got 2 angles which are 90, so a+d+90+90 = 360

near burrow
#

oh

#

so

#

why does b + c = a

fallen mantle
near burrow
#

hmph

#

i dont know why i dont get it

#

so

#

which 2 angles are 9

#

90

fallen mantle
#

PQR and PSR are both 90

near burrow
#

why

fallen mantle
#

rmb that: PQR + QRS + RSP + SPQ = 360

fallen mantle
near burrow
#

oh

#

OH

#

so

#

left side

#

and bottomleft side

#

and right side, bottom right side are 90

#

you

#

are in

#

a taken channel

sick plank
#

oh sorry

near burrow
#

go there

#

and try

#

okay so

#

anonymous

fallen mantle
#

yes

near burrow
#

uhhh

#

idk where would i learn this

#

just written and explained simply in text form

#

i just cant understand it and ive got an even harder next question

obtuse pebbleBOT
#

@near burrow Has your question been resolved?

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tepid timber
#

Heyo

obtuse pebbleBOT
tepid timber
#

Just wanted to clarify minor details for finding the determinant of a matrix

#

To find the determinant of a matrix, we just use laplace expansion on the top row of the matrix right?

#

And then that's all?

mental solstice
#

or any row or column, really

tepid timber
#

Wait wat rlly

#

So I can apply it to any single row or column

#

And it would find the determinant of the matrix

mental solstice
#

yes, so it's always a good idea to pick a row or column with a lot of zeroes

tepid timber
#

Oh

#

I see, thank you so much :))

mental solstice
#

no prob ๐Ÿ™‚

tepid timber
#

.close

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sleek sinew
obtuse pebbleBOT
sleek sinew
#

Are these triangles similar? I rotated it two different ways

#

One was similar, one was not

#

Just not sure which line segment UG corresponds to

#

If we make it correspond to FE, then SAS says the triangles are similar

#

But is it possible UG corresponds to BE, resulting in not similar?

tepid timber
#

I believe it is similar

#

angle UGA = angle BEF

#

UG/EF = GA/BE

#

The ratios of two lines and a corresponding angle is similar

#

And I think that's one of the proofs for similar triangles? I really don't trust myself

sleek sinew
#

Yes that would be correct if we did it that way

#

Just wondering how we know for sure UG corresponds to EF

#

Because if we did UG/BE = other ratio, it will not work

tepid timber
#

Yeah since UG/BE doesn't work and UG/EF works, then UG corresponds to EF

#

Cus if u said triangle ABE is similar to triangle PLO for example, AB/PL = BE/LO

#

And AB/LO wouldn't be equals to PL/BE

sleek sinew
#

Okay thanks

#

.close

obtuse pebbleBOT
#
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obtuse pebbleBOT
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rapid sentinel
#

need help solving 1 and 3 please, asap

obtuse pebbleBOT
rapid sentinel
#

i looked up the first one but didnt understand anything too

fallen mantle
warm shaleBOT
river zephyr
#

Oh lol very similar question to mine

#

If itโ€™s above x axis, discriminant is <0

#

So arrange the equation to b^2-4ac <0

rapid sentinel
#

a and c are both gonna be 1 yes?

river zephyr
#

No

#

C is k

rapid sentinel
#

ah i see

#

i get k<9

river zephyr
#

Hmm

#

It should be k>9

#

Do you have the mark scheme with you by any chance

rapid sentinel
#

yes

river zephyr
#

Whatโ€™s the answer?

rapid sentinel
#

its k>9

river zephyr
#

Ok one sec

#

Ok so when u multiply negative on both side of inequality

#

The inequality change sides

rapid sentinel
#

ohhh

#

i get it now

#

how do i do the second part

river zephyr
#

Is the answer k=11 ?

rapid sentinel
#

yes

river zephyr
#

Ok since the line intersects with curve

#

At one point bc tangent

#

U can equate the two equation

#

The line and curve equation, combine it into one

rapid sentinel
#

mhm

river zephyr
#

after than u should get a quad equation

#

Then u can use discriminant on it

#

Since itโ€™s a tangent and touches at one point only

#

B^2-4ac=0

#

U should get k=11 after that

rapid sentinel
#

yea got it

#

tysm

river zephyr
#

Np

rapid sentinel
#

in the 1st part of the 3rd question i do the same?

#

equal the both equations and solve them?

#

no. 3

obtuse pebbleBOT
#

@rapid sentinel Has your question been resolved?

rapid sentinel
#

<@&286206848099549185>

obtuse pebbleBOT
#

@rapid sentinel Has your question been resolved?

obtuse pebbleBOT
#

@rapid sentinel Has your question been resolved?

obtuse pebbleBOT
#
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spiral yoke
#

so i got -30 in this question but it was incorect 5(a โ€“b) if a = โˆ’4 and b = โˆ’2

rocky goblet
#

be careful with negatives

spiral yoke
#

?

rocky goblet
#

you're subtracting negative two

spiral yoke
#

so -6

rocky goblet
#

no

#

this is why you have to be careful

#

think about it: if you take 2 and add negative 2, what do you get

spiral yoke
#

?

rocky goblet
#

what's 2 + -2

spiral yoke
#

0

rocky goblet
#

yep, it's 0

#

2 + -2 is the same as 2 - 2

balmy mortar
#

$a-b = a+(-b)$

warm shaleBOT
spiral yoke
#

ok

#

so 4+(-2)??

rocky goblet
#

so if 2 + -2 is 2 - 2 which is 0
what should 0 - -2, subtracting negative two from zero, be?

spiral yoke
#

2

rocky goblet
#

yep

#

subtracting -2 is the opposite of adding -2, and adding -2 is subtracting 2, so subtracting -2 is the same thing as adding 2

warm shaleBOT
balmy mortar
#

-(-a) = -1 * -1 * a = 1 * a = a

rocky goblet
#

so now if we go back to -4 - -2

#

subtracting -2 is the same as adding 2, so this is -4 + 2

spiral yoke
#

-2

rocky goblet
#

yep

spiral yoke
#

soo -10

rocky goblet
#

-4 + 2 = 2 + -4 = 2 - 4 = -2

#

and then yeah multiply that by five

spiral yoke
#

ok thx for the help

#

.close

obtuse pebbleBOT
#
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rich holly
#

was it a mistake adding all 4 equations?

obtuse pebbleBOT
empty cypress
rich holly
#

find the value of P(5)

balmy mortar
#

consider a polynomial Q

#

which has something to do with P

#

is my hint...

#

Q = P + ???

rich holly
#

uhh

#

no idea

balmy mortar
#

Let Q(x) = P(x) + R(x)

#

where R(x) is a polynomial to find

#

there is a sensible choice

rich holly
#

so P(5)

#

R(x)=P(5)

balmy mortar
#

how is that a polynomial

#

well i guess it is

#

P(5) is just a constant though

rich holly
#

hmm yeah

balmy mortar
#

Q(x) = P(x) - P(5)

#

how will this help (it wont)

#

You try it out and see if u get anywhere.

balmy mortar
rich holly
warm shaleBOT
#

hyperlix26

balmy mortar
#

It is.

#

a b c d are constants

rich holly
#

yeah

#

and how would Q(x) = P(x) + R(x) help me?

#

what's R(x)?

balmy mortar
#

Read what I said

rich holly
#

I know what P(x) is

balmy mortar
#

I said you have to find a suitable R(x)

#

that is helpful

#

That is my hint

rich holly
#

idk what the suitable R(x) is, wanted to make it equal to $(5)^4+a(5)^3+b(5)^2+c(5)+d$ but you said it wasn't equal to P(5) so that's not it

warm shaleBOT
#

hyperlix26

balmy mortar
#

skdjfnfkiffifofofofkfkfifo

#

Dont give up before you've even tried

rich holly
#

what

balmy mortar
#

oh nvm misread

#

I told you though

#

to find a suitable polynomial R(x)

#

And I also said it isnt complicated, it is simple

#

Write down a few guesses, see if they could help you any way.

#

If youre stuck, then say what R have you tried

rich holly
#

yeah nope

#

nothing else makes sense to me except for $(5)^4+a(5)^3+b(5)^2+c(5)+d$

warm shaleBOT
#

hyperlix26

rich holly
#

other than that I'm just making stuff up

#

if R(x) is a polynomial to find, why not make R(x)=Q(x)-P(x)?

balmy mortar
#

of R

#

Do you understand what a polynomial is?

rich holly
#

yeah

balmy mortar
#

I hinted a polynomial, so please realise it probably isnt a constant

#

So what example of R could you try

#

just name one

#

any

rich holly
#

the same as P(x) but it doesn't make sense

balmy mortar
#

...

#

Tell me an example

#

of ANY polynomial

rich holly
#

P(x) is a polynomial

balmy mortar
#

omg

#

can you keep it simple?

rich holly
#

ax+b?

balmy mortar
#

if i randomly asked you for an example of a polynomial you wouldnt give me that

#

why the letters???

rich holly
#

it still counts right?

balmy mortar
#

An explicit example please?

rich holly
#

2x+7?

balmy mortar
#

Yes. Good.

#

Now I asked you to consider the new polynomial Q(1) = P(x) + 2x+7

#

What can we say using the given information?

#

It must still be of degree 4

#

But in particular what is Q(1) and so on

rich holly
#

1+2+7

#

that's Q(1)

#

which is 10

balmy mortar
#

indeed

#

and you can compute Q 1 2 3 4

#

yes?

rich holly
#

yeah

balmy mortar
#

Now my hint was to pick a nice R(x)

#

what 'nice' means, try to figure it out

#

I will say now that Q(1) = 10 isn't helpful, so we need a better R

rich holly
#

yeah I'm figuring out how to find a better R

balmy mortar
#

Q(1) = ?
Q(2) = ?
Q(3) = ?
Q(4) = ?

First maybe think what we want these to be

#

for some useful information

#

Then you can find a good R

rich holly
#

ok if I said we want those to be 0, how would it help?

balmy mortar
#

If you know Q(1) = 0

#

What does this tell you about Q?

#

Is there a theorem you can use perhaps?

rich holly
balmy mortar
#

(x - 1)

rich holly
#

oh

#

1 is a zero of the function?

balmy mortar
#

well yes

#

so the theorem you can use is?

rich holly
#

no idea

balmy mortar
#

Factor theorem

#

Remainder theorem

#

surely you have done either?

rich holly
#

maybe

balmy mortar
#

Review it then

#

otherwise you'll be stuck

rich holly
#

I don't know what they are called here

balmy mortar
#

For a polynomial f
f(a) = 0 <=> (x-a) is a factor of f(x)

#

For a polynomial f
f(a) = k <=> f(x) = (x-a)g(x) + k for some g

#

Factor and remainder theorems

rich holly
#

yeah I've seen them but I don't understand them enough

#

if you can divide a polynomial by (x-a) and the result is 0, then (x-a) is a factor right?

balmy mortar
#

no...

rich holly
#

what

#

why

balmy mortar
#

if i divide a polynomial by another polynomial I won't get 0

#

unless the original polynomial is 0

#

???

rich holly
#

I mean the remainder

balmy mortar
#

yh ok but thats just restating what i said

#

Try applying the theorem to this problem...

rich holly
#

yeah basically that's all I know, I don't understand much from the remainder theorem

rich holly
balmy mortar
#

did you see me suggesting such a method?

rich holly
#

no

balmy mortar
#

Why would you end up doing such a thing in the direction I've been hinting at

balmy mortar
#

in your working

#

theres just 1

#

you mean 4 equations i suppose...

rich holly
#

oh equations

#

yeah

obtuse pebbleBOT
#

@rich holly Has your question been resolved?

obtuse pebbleBOT
#
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brittle swan
#

how do we solve
$a_n = 3 a_{n - 1} + 10?$

obtuse pebbleBOT
warm shaleBOT
#

Chromium

spiral maple
#

what's the initial condition?

#

just a_0?

brittle swan
#

oh uh

#

nth

#

.close

obtuse pebbleBOT
#
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balmy mortar
#

rifififififfg you hibihgigog ficicciciocovo

spiral maple
#

Ok then.

obtuse pebbleBOT
#
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compact shadow
obtuse pebbleBOT
compact shadow
#

.close

obtuse pebbleBOT
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late pond
#

Hey everyone,
I need to calculate the radius and height of a cylinder, where the materiale usage is $20m^2$
The material usage can be calculated using this formula:
$O(r)=10\cdot r^{-1}+\pi+r^{2}$

I would assume that I could put 20 instead of $O(r)$, then isolate the radius $r$ but that gives me 3 solutions:
$20=10\cdot r^{-1}+\pi+r^{2} = $
r=2.221046 or r=โˆ’2.743439 or r=0.522393

warm shaleBOT
obtuse pebbleBOT
#

@late pond Has your question been resolved?

potent dagger
#

hello

#

by material usage does it mean the material used to cover the whole cylinder

obtuse pebbleBOT
#

@late pond Has your question been resolved?

obtuse pebbleBOT
#
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obtuse pebbleBOT
late pond
#

@potent dagger

#

<@&286206848099549185>

potent dagger
#

if that's the case then u could try using the formula for total surface area of cylinder

#

and equate it to 20

#

then you'd get values for the height as well

late pond
#

Is it this one?

#

$V=\pi \cdot r^{2}\cdot h$

warm shaleBOT
late pond
#

@potent dagger

potent dagger
#

no no

#

not the volume, i meant the surface area

#

volume has units of m^3

#

not m^2

late pond
#

Yeah ๐Ÿ™‚

potent dagger
#

the formula should be 2pir(r+h)

late pond
#

Yeah, but that gives me 2 unknowns (radius and height)

potent dagger
#

you do have two radius values tho

#

from what you solved earlier

#

tryin using each value and see what value of height u get

#

by using the equation we just discussed rn

late pond
#

Okay.

#

I have these two radius: r=2.221046 or r=0.522393

#

$20 = 2\cdot \pi \cdot 2.221046\cdot (2.221046+ h)$

warm shaleBOT
late pond
#

and

#

$20 = 2\cdot \pi \cdot 0.522393\cdot (0.522393+ h)$

carmine bear
#

Was the equation in the question given by the question or is it something you deduced

warm shaleBOT
late pond
#

This one was given in the question:

carmine bear
#

well you could create 2 simultaneous equations

#

one using O(r) = 20 and the other using surface area = 20

#

unless O(r) comes from the surface area equation in which case that probably won't work

#

essentially what im trying to say (or hope will work) is if you try to solve $$20 = 10r^{-1} + \pi r^2$$ $$20 = 2\pi r(r+h)$$

warm shaleBOT
#

I can't believe you've done this

carmine bear
#

simultaneously

#

not sure if it will work but worth trying

#

like perhaps try finding an equation for $r$ using the first equation and then sub replace both $r$ in the second equation with the one you got from the first one

warm shaleBOT
#

I can't believe you've done this

obtuse pebbleBOT
#

@late pond Has your question been resolved?

obtuse pebbleBOT
#
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rocky dove
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Hello everyone! I am just struggling on how to find critical points with e problems ๐Ÿฅฒ not sure if I am doing it right. Is it truly possible to not have critical points? If so what to do?

obtuse pebbleBOT
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@rocky dove Has your question been resolved?

rocky dove
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<@&286206848099549185>

obtuse pebbleBOT
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@rocky dove Has your question been resolved?

compact shadow
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Use x=rcos(t), y=2rsin(t)

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That becomes e^{-r^2sin(2t)}

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Maximum when r=1 and sin(2t)=-1,minimal when r is 1 and sin(2t)=1

rocky dove
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okay and I assume that helps me find the critical points

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ooof okay i see what you are getting at

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my question is how did u know that y=2rsin(t)? it just is? or its coming from a formula

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just curious

compact shadow
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?

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You donโ€™t know sin(2t)=2sin(t)cos(t)?

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This is all I used

rocky dove
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its been a while ;-;

compact shadow
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sin(x+y)=sin(x)cos(y)+cos(x)sin(y) then let x=y=t

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You have sin(2t)=2sin(t)cos(t)

rocky dove
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ohhh

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thank you so much!

compact shadow
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Np

rocky dove
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.close

obtuse pebbleBOT
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Channel closed

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Use .reopen if this was a mistake.

obtuse pebbleBOT
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ashen sierra
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The question: Solve tanยฒฮธ = 2 * 1/cosฮธ for 0ยฐ โ‰ค ฮธ โ‰ค 360ยฐ.

The answer in the book was: 64.3ยฐ, 295.7ยฐ, 219.9ยฐ and 140.1ยฐ.

ashen sierra
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Here's my working out. Idk what I did wrong

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<@&286206848099549185>

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oh well .close

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.close

obtuse pebbleBOT
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cosmic moon
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I am stuck on part E. I am doing past paper questions and I am confused on how I am supposed to do this

short spruce
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what have you tried

cosmic moon
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Honestly, looking at the question hade made me not try but from the rules I know of, I can't think of a way to do it

short spruce
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i assume you know exponent laws? if not, google them

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hint: rewrite 1/(9^x) with a base of 3

cosmic moon
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I got 1/3^2+x

short spruce
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?

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how so

quartz mica
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how

cosmic moon
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Well, I learned exponent laws recently so there might be a flaw in my method but what I basically did was I assumed that since I can write 9 as 3^2, and when you multiply indices together you add the power so that's what I did

quartz mica
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the 1/9 means 9^-1

short spruce
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refer back to your exponent laws

quartz mica
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ye[p

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good luck aqua man

short spruce
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actually i think you just interpreted it incorrectly

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you rewrote $9$
as $3^2$, yeah, but that gets you $(3^2)^x$

warm shaleBOT
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a disappointing son

short spruce
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the law you tried to apply states $a^b\cdot a^c=a^{b+c}$

warm shaleBOT
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a disappointing son

short spruce
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but you're raising an exponent to an exponent here, not multiplying

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we've already established that. this isn't your problem

quartz mica
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sorry again

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that was inapropriate of me

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@cosmic moon do you know how to convert 1/9x to an exponent

cosmic moon
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I did some working out, and got $3^2x-a+2^x$ = $3^2y-x$

warm shaleBOT
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AquaDrix

cosmic moon
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This basically

quartz mica
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now you can cancel the 3s

short spruce
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that ain't right

quartz mica
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so it becomes 2x - 1 + 2x = 2y

quartz mica
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i thought the same thing

short spruce
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also that's wrong

quartz mica
short spruce
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that's not up for debate, i am looking at the work you did for him

quartz mica
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i guess

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i did some

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mb

obtuse pebbleBOT
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@cosmic moon Has your question been resolved?

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Channel closed

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sturdy ledge
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(Use a Double- or Half-Angle Formula to solve the equation in the interval [0, 2๐œ‹). (Enter your answers as a comma-separated list.)
tan(๐œƒ) + cot(๐œƒ) = 4 sin(2๐œƒ)

strong vale
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Let's start by getting all the trig functions in terms of theta

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How do you get sin(2theta) in terms of just theta

sturdy ledge
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u change it to sin(theta)cos(theta)

strong vale
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yh

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but $\sin{2\theta} \not= \sin{\theta}\cos{\theta}$

warm shaleBOT
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azeem321

sturdy ledge
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i meant 2sin(theta)cos(theta)

strong vale
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good

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now we have

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$\tan{\theta} + \cot{\theta} = 8\sin{\theta}\cos{\theta}$

warm shaleBOT
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azeem321

sturdy ledge
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yep

strong vale
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now what

sturdy ledge
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now u change tan and cot to sin(theta)/cos(theta) and cot to cos(theta)/sin(theta)

strong vale
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good and after doing that how about multiplying both sides by $\sin{\theta}\cos{\theta}$

warm shaleBOT
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azeem321

strong vale
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Giving $\sin^2{\theta} + \cos^2{\theta} =8(\sin{\theta}\cos{\theta})^2$

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now what

sturdy ledge
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distribute the 8?

warm shaleBOT
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azeem321

strong vale
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sorry i made a typo

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now what

sturdy ledge
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square root both sides

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?

strong vale
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what is s^2+c^2

sturdy ledge
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1

strong vale
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Can you solve it now?

sturdy ledge
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umm tbh no thats the part im stuck on

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I turned that into 1/2=(sin(2theta))^2

strong vale
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good

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So now you must solve $\sin{2\theta} = \pm \frac{1}{\sqrt{2}}$

warm shaleBOT
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azeem321

strong vale
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u can do this now?

sturdy ledge
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which I get pi/8 and -pi/8

strong vale
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notice the domain

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and remember sin(2x) is periodic

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with period pi

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which means u can add/subtract pi

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and it will be a solution

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so if x=a is a solution

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x=a+pi is a solution

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x=a+pi+pi is a solution

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x=a-pi is a soluition

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but the question only wants the solutions between 0,2pi

sturdy ledge
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we just add pi to both of them until we get all the possible solutions in the domain?

strong vale
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let's put this on a back burner

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let me show u something important

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this is the graph of sin(x)

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Suppose we want to find all values of x, for which sin(x) = a

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we know there is a solution at the red line

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How do you get the second solution?

sturdy ledge
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the next point where they intersect

strong vale
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yh

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but most calculators won't give you that solution

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so what algebra can u do to get that solution

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look at the symmetry of the curve

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$\sin{x} = \sin({\pi-x})$

warm shaleBOT
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azeem321

sturdy ledge
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origin symmetry

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?

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so its odd

strong vale
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Notice that the curve is the same either side of the red line

sturdy ledge
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ohhhh

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I take pi minus what I got?

strong vale
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That would be for just sin(x)

sturdy ledge
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to get the other answer

strong vale
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But since since we have sin(2x)

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You do $\frac{\pi}{2}- \frac{\pi}{8}$

warm shaleBOT
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azeem321

sturdy ledge
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because the period was half of what it was before?

sturdy ledge
strong vale
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So for $\sin{2x} = \frac{1}{\sqrt{2}} \implies x = \frac{\pi}{8}, \frac{3\pi}{8}$