#geometry-and-trigonometry

1 messages Β· Page 55 of 1

dark sparrow
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"sec is cos" is misleading at best, or just false at worst

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well if you meant reciprocal then you have to say reciprocal lmao.

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sec(x) = 1/cos(x)

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but you cannot just drop the "1/..."

wispy jewel
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Still yet to understand Maths English, My teacher told me it's a whole different playing field πŸ€¦β€β™‚οΈ

upper karma
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try using properties of triangles

lime dune
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"maths english" no this is just "basic communication"

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say exactly what you mean and mean exactly what you say

faint pasture
wispy jewel
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So...

lime dune
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there's nothing particularly deep to explain, it's just plugging into the definitions of your trig ratios

upper karma
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this question is from "properties of triangles" topic

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oh a, b and c are sides of a triangle

faint pasture
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πŸ’€ shoulda said so- yea so the problem is solved now if i consider it as an angles of a triangle

upper karma
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and A is the angle opposite to side with length a

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and B is the angle opposite to side with length b

faint pasture
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iseee

upper karma
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why tf do they make these questions ambiguous

faint pasture
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tbh they gave us enough context imagine if they had to write everything there book would like a billion pages

upper karma
faint pasture
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ill try it again a bit later

upper karma
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alr

fast oriole
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forgot mos stuff

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so i need recap

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nvm

strong hearth
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How?

fast oriole
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changed question

silent plank
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what's your issue here

fast oriole
silent plank
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look up geometry notation

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also wacth their video guide

dark sparrow
# strong hearth How?

apply difference of squares to num and denom separately, and you will get some tan(a+b) simplifications afterward.

obsidian hornet
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Hi everyone, I would like to ask about one type of problem associated with power of the point, when you can rotate chord in circle and get another 4 points that lie on one circle. For example, I have problem like this: given a parallelogram with configurations as in the picture and you need to proof that 4 points (2 vertices of the parallelogram, the bases of the perpendicular and the continuation of the median) lie on one circle. So, does anyone know problems with a similar idea?

dark sparrow
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what kind of file is that?

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can you reupload properly

proud obsidian
faint pasture
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Yall might have just downloaded malware-

dark sparrow
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i did not download it

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i saw that it is a file with no extension, and for this reason alone i raised the suspicion

obsidian hornet
proud obsidian
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here is his problem

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nvm he sended it

faint pasture
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Nice

grave pond
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(I removed one of the copies)

faint pasture
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How do i find the maximum and minimum in problems like this one generally?

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The official solution is just hit and trial

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But there gotta be a better way

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And like how would i do it if i had to find the minimum instead of just its sign?

nocturne remnant
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you can convert it into a geometry problem

proven summit
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Is it postive

proven summit
nocturne remnant
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?

faint pasture
faint pasture
proven summit
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are u familiar with inverse trigonometry

faint pasture
nocturne remnant
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actually nvm now that i think about it doesnt really work

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yeah

faint pasture
proven summit
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oh fuck it said minimum

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For max what I did is put 2 of them as pi/2 one as 0

nocturne remnant
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well you can just prove that it is negative at some point, then you've proved that the minimum must be negative (since the minimum must exist as the expression is lower bounded by -3)

faint pasture
proven summit
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for minimum it could be
Ο€+Ο€-Ο€

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Does that satisfy

faint pasture
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(for min the book did -pi/2, -pi/2 and 2 pi but why)

proven summit
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oh wait it doesn't

faint pasture
proven summit
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yea

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I have done a similar question

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But of invese trigonometry

faint pasture
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hmmm

proven summit
faint pasture
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this was in amit m agarwal

proven summit
faint pasture
proven summit
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I just have the calculus one

faint pasture
proven summit
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With Domain range I think

faint pasture
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like sure the sign determination is ez

proven summit
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Ye

faint pasture
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but finding the exact value

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howd we do that

proven summit
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Lemme see it

faint pasture
proven summit
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I think

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As it's alpha beta gamma

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U can replace it with sin^(-1)

faint pasture
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nope

proven summit
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so the limited domain becomes from (-Ο€/2 , Ο€/2)

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for all

faint pasture
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cuz alpha beta gamma dont have to fit the range of sin inverse

proven summit
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But it says sinA= x

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then A could be sin^-1 x

faint pasture
proven summit
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sin^-1 has a restricted domain

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[-Ο€/2 , Ο€/2]

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Sorry range

faint pasture
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ye so thats why we cant use it in this problem ig

proven summit
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Restricted range

upper karma
faint pasture
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since even the official solution included, -pi/2, -pi/2, 2pi

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so ye

faint pasture
proven summit
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Else if u don't consider that there could be infinite values of a b c

proven summit
faint pasture
proven summit
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Resulting value of sina + sinb+ sinc

faint pasture
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yea

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sure we could write c = pi - b- a and get an eq in 2 variables but i dont see what i can do further

proven summit
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not gonna work

faint pasture
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hmmm

upper karma
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sin(a+b) is sinAcosB + cosASinB

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Sin C + Sin D is 2SIN(C+D/2)*cos(C-D/2)

faint pasture
faint pasture
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like how am i supposed to think of that in an exam setting

upper karma
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wait

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its something related to

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nvm

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1

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ig

faint pasture
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yea πŸ’€ what was you approach?

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multiplying and dividing by tan54*tan18 ig?

upper karma
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yeah

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i think ivbe done this before

faint pasture
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yea πŸ’€ like how tf am i gonna think of that in an exam setting

upper karma
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its some shitty

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identity

faint pasture
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our tchr gave that one to us in the class none of us solved it

upper karma
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what grade

faint pasture
upper karma
faint pasture
upper karma
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im in 9th πŸ’€

faint pasture
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like trig can be fun but dont ask shit like that in an exam bruh-

faint pasture
upper karma
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i learnt trig when i was in class 8

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like

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identities

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and all that

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i forgot most of it

faint pasture
upper karma
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  • kv
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fucked up

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franchise

faint pasture
upper karma
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i can solve trig equations

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i struggle with application of trig

faint pasture
upper karma
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things that includes triangles

upper karma
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10th is super basic

faint pasture
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you will get thru it though you have plenty of time

upper karma
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im only able to deal with questions including sin cos and stuff

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when i get question with finding the length of the triangle

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idk what to do

faint pasture
faint pasture
upper karma
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where can i use actual calculus?

faint pasture
faint pasture
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and like proper coordinate geometry

upper karma
faint pasture
upper karma
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who cares abt graphs

faint pasture
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main use of calculus is to extract information from graphs

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areas tangents and stuff like that

upper karma
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in physics

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?

faint pasture
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thats what integration fundamentally means

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to find the area under the graph

upper karma
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shit

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i dont likee graphs

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i dont like geometry

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the whole thing is

faint pasture
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πŸ’€ lmaoo thats why you dont just mug up formulae

faint pasture
upper karma
faint pasture
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sure you probably might not know the significance of what you are doing

upper karma
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in trigonometry

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how tf am i supposed to know that i multiply the equation by fucking 3/2*2/3 to get the answer

faint pasture
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but just the feeling of successfully solving an integral or a limit you spent hours on is satisfying

faint pasture
faint pasture
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there are so many integrals you just cant solve in less than like 10 mins at least even if you know the idea behind them

upper karma
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i cant solve integrals which includes more than 2 terms

faint pasture
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like you couldnt solve sin^3(x) cos^2(x) sec^2(x)cosec^3(x)?

upper karma
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i dont remember trig functions

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i do some

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sin x is

faint pasture
upper karma
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-cosx

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wait

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cosx is

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-sinx

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sec idk

obsidian harness
upper karma
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maybe cosectan

upper karma
faint pasture
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nope

obsidian harness
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(sin x)' = cos x

obsidian harness
upper karma
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yea

faint pasture
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you can slow down

upper karma
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i remembered those two

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cause i used them in differentiation

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basic

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idk others πŸ’€

faint pasture
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why is derivative of sin(x) equal to cos(x)

upper karma
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never used

faint pasture
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?

obsidian harness
upper karma
obsidian harness
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It follows pretty nicely from the series definition

upper karma
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maybe graph

faint pasture
faint pasture
upper karma
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sin/cos = tan

faint pasture
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learn, dont mug up

faint pasture
faint pasture
upper karma
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inmaginary and real

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is complex

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simple

faint pasture
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(but for him i was expecting him to use the basic limit defniition of derivative)

upper karma
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i dont know limits

faint pasture
upper karma
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lim x => 0

obsidian harness
upper karma
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i forgot

faint pasture
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sure i get the feeling of wanting to be the best

upper karma
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im in a valorant game

faint pasture
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lmfao

upper karma
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ok

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now im free

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lets talk

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elderly talk

faint pasture
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slow donw

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get you basics clear

upper karma
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wdym slow down

faint pasture
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by basics i mean trig + limits

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then try calc

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if you have interest then continue

upper karma
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i mug up shit

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done

faint pasture
faint pasture
upper karma
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127.0.0.1

faint pasture
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why include localhost

upper karma
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localhost

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idk

faint pasture
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send me your real ip

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πŸ—Ώ

upper karma
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1.618.69.420

faint pasture
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what will i do with localhost-

upper karma
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here

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what do i need for ioqm

faint pasture
faint pasture
upper karma
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wait i need water

faint pasture
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idk i skipped all of calc and geo

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number theory nd pnc are the simplest topics for olympiad math

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but yea your choice

upper karma
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i dont like geomtry

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fucking

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1000 rules

faint pasture
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anyways you aint clearing ioqm by mugging up shit anyways

upper karma
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on two fucking lines

upper karma
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i can solve some ioqm pyqs

faint pasture
upper karma
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whtg grde are u

faint pasture
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11th

upper karma
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if i score 2 without any preps?

faint pasture
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i was scoring in 20s in mocks

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but in the real exam i got 15

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so yea

upper karma
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in 11th?

faint pasture
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9th

upper karma
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u got the certificate

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where did u rep

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prep

faint pasture
faint pasture
upper karma
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kids write shit in their bio to look cool

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ffs

faint pasture
upper karma
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i know from where sin(a+b) came

faint pasture
upper karma
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tell

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bro

faint pasture
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sin(a+b) proof is weird enough anyways lmao

upper karma
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u dont want me to progress

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thats why u arent telling me

upper karma
faint pasture
upper karma
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pls tell

faint pasture
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give the 2022 paper

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tell me how much you score

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then ill see

upper karma
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ok

faint pasture
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(2022 cuz i was in 9th when i gave it)

upper karma
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i onkly find paper with answers

faint pasture
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if you cheat then whats the point

modest garnet
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Hello

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Anyone has some trigonometry questions

worldly swan
modest garnet
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Yes please

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Normal questions

worldly swan
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you will find some here

upper karma
faint pasture
trail tendon
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but also i wouldnt know if i would consider knowing how to solve basic integrals without knowing what limits are "doing calc"

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i mean i guess technically

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xD

faint pasture
trail tendon
faint pasture
obsidian harness
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You could be green by now

faint pasture
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(also im dumb enough cant help others-)

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and dont have enough patience to solve the easier problems

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i help ppl in calc tho sometimes

empty yew
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Is the domain of the equation $\frac{\sin\theta}{1+\cos\theta}$ $\mathbb{R}-{2n\pi\pm\pi}$?

somber coyoteBOT
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KingDanger

faint pasture
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(hence why i said rare wolfram l)

empty yew
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Ok

obsidian hornet
# modest garnet Anyone has some trigonometry questions

If you don't mind problems with geometric overtones, then I can suggest proving that the perimeter of an orthotriangle is 2Rsinasinbsinc, where R is the radius of the circumscribed circle of the original triangle and a,b,c-angles.

inner vapor
faint pasture
trail tendon
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is it just a bad picture?

faint pasture
trail tendon
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it says "regular" pentagon, doesnt that mean the angles/sides supposed to be

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yeh

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☠️

faint pasture
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i mean it usually says the figures arent gonna be to scale

trail tendon
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it looks like it was drawn by a 5 year old

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or me

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πŸ’€

faint pasture
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there is no way i could draw a straight line

inner vapor
trail tendon
inner vapor
faint pasture
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and regular pentagon

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also given

trail tendon
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and all sides are same

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even though they cant draw

faint pasture
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(you really need to work on your definitions before attempting amc)

inner vapor
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ae=ba???????

trail tendon
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ae and ba are sides of the pentagon

inner vapor
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okay

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,w 108-60

upper karma
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screaming crying

twin spindle
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Is someone able to help w using the period, for evaluation?

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Cause all of these examples are confusing me tbh πŸ’€

hard moon
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for any number x, sin(x + 2Ο€) = sin(x)

Similarly for any number x, cos(x + 2Ο€) = cos(x)

So for example, let’s say you want to figure out sin(9Ο€/4). Then this is an example where this rule is useful. To see why, we know 9Ο€/4 = Ο€/4 + 2Ο€. Thus, sin(9Ο€/4) = sin(Ο€/4 + 2Ο€) = sin(Ο€/4) = sqrt(2)/2

hard moon
twin spindle
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Ohhhh i see mow

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Now*

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Because 9pi/4 is jus equivalent to pi/4

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Since you do a whole revolution and then a pi/4 of a revolution

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Right?

hard moon
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yeah, so the problems you probably encountered before these ones were evaluating sine and cosine at angles between 0 and 2Ο€

But these rules allow you to deal with angles outside of that range, so you can evaluate sine and cosine of angles less than 0 (say sin(-Ο€/3)) and sine and cosine of angles greater than 2Ο€ (say sin(17Ο€/4))

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So say you want to find sin(17Ο€/4)

As you said, you basically just do a whole revolution of 2Ο€, and the sine value will remain the same

So putting this rule in action, we have sin(17Ο€/4), but the angle is too big, so let’s move 2Ο€ backwards - - so we see this is the same as sin(9Ο€/4) - - still too big, so we move 2Ο€ backwards again - - this is the same as sin(Ο€/4), and since Ο€/4 falls within the range of 0 and 2Ο€ (and it’s one of the nice angles on the unit circle), we surely can evaluate it

inner vapor
slow sundial
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how do i calculate the angle of this

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or simply whats the angle

hoary totem
inner vapor
#

?

rustic grove
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I doubt answer is wrong

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Anybody?

deft sail
# slow sundial how do i calculate the angle of this

If you add all the angles of a pentagon, it’s 540Β° .two of them are ninety. If you subtract them it’s 360Β°. There is a triangle at the bottom. Use the sine or cosine theorem. It’ll find the angle degree

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That’s what I think

north kindle
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This problem is giving me a lot of trouble, I’ve tried messing around with it but can’t find anything

lime dune
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see that perpendicular that stops suddenly?

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what if you extended it to hit WV?

hoary totem
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^

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then what do you know about the angles of a parallelogram?

hoary totem
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once u extend the perpendicular line like so

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you can solve it pretty easily

north kindle
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I didn’t

hoary totem
north kindle
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It’s a right angle?

hoary totem
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PYH? check again

north kindle
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I don’t know

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I don’t even know what angle you are talking about

hoary totem
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angle PYH

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thats how angles are named, with 3 points, the vertex of the angle is the middle letter

north kindle
#

Ah

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I don’t know

hoary totem
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so for example in the diagram they give u that angle ZWV = ZWP = PWZ = VPW = 140 degrees

hoary totem
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opposite angles will be the same

north kindle
#

I know

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Oh it’s x

hoary totem
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yes

north kindle
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I didn’t see that there

hoary totem
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ok so now
we know PYV is 3x
and PYH is x
so HYV is?

north kindle
#

140-4x?

hoary totem
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not quite

north kindle
#

Or wait

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140-5x?

hoary totem
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check what angle im talking about again

north kindle
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Oh

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2x

hoary totem
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yes

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we can express HYV in another way

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and that allows us to solve for x

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do u think u can try to find it?

north kindle
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Oooh I have an idea

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Wait no, that would require a theorem I haven’t proven yet

hoary totem
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what theorem would that be?

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what was your idea?

north kindle
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The sum of the angles of a triangle being 180 degrees

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I was gonna do something with the triangle HVY

hoary totem
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cool idea but u dont need that here if u dont wanna use that

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u can do it solely within the parallelogram

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we're given that angle ZWV is 140 degrees
and also that angle ZYH is 90 degrees
try to use that in order to express HYV in another way

north kindle
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Oh wait

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It’s 140-90

hoary totem
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exactly good job

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so now x is?

north kindle
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25?

hoary totem
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yes πŸ‘

north kindle
#

Nice

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These are hard lol

hoary totem
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and im sure u will gain that intuition

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fast

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lmao

north kindle
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Nahhhh

hoary totem
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ur actually a genius

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i think ull find geometry pretty fun

north kindle
#

I’m not escpecially smart I don’t think

hoary totem
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ur pretty smart

north kindle
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Nahhhh

crimson arrow
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how do I find the reference angle of cot(180)?

hoary totem
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well cotangent of 180 degrees is not an angle

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its.. undefined

crimson arrow
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okay and what about the exact function value?

hoary totem
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its undefined

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notice that cotangent is given by cosine/sine

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and cosine 180 degrees is -1
sine 180 degrees is 0

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so cotangent 180 degrees is -1/0

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ur dividing by zero here which isnt allowed

crimson arrow
#

okay, draw the reference angle and find the exact function value if it exists of Sec(-270)?

crimson arrow
#

If sina= 5/13 and sinB= 12/13, where a and B are between 0 and Ο€/2, evaluate sin(a-B) and cos(a+B).

hoary totem
#

i tried proving it, this is my proof:

  • let:
    A, B, C be points on a sphere with center O and radius OA = OB = OC = 1

  • draw:
    CA' and CB' to be tangents of the sphere at C in direction of A and B respectively
    then A'CO and B'CO = 90 deg.

  • draw:
    extend OA and OB until they intersect CA' and CB' respectively.
    call the intersection points A' and B' respectively.

  • denote:
    A = CAB B = ABC C = BCA
    a = BOC b = AOC c = AOB
    a' = CB' b' = CA' c' = A'B'

  • planar law of cosines on triangle A'CB' gives:
    c'Β² = a'Β² + b'Β² - 2a'b'cos(C) [1]

  • from definition of tan(x), and since A'CO = B'CO = 90, and OC = 1:
    a' = tan(a) [2]
    b' = tan(b) [2]

  • [1] and [2] together make:
    c'Β² = tanΒ²(a) + tanΒ²(b) - 2tan(a)tan(b)cos(C) [3]

  • pythagorean theorem on triangles A'OC and B'OC along with [2] give:
    A'OΒ² = 1 + tanΒ²(b)
    B'OΒ² = 1 + tanΒ²(a)

  • apply the trig identity 1 + tanΒ²(x) = secΒ²(x):
    A'OΒ² = secΒ²(b) [4]
    B'OΒ² = secΒ²(a) [4]

  • square root both sides:
    B'O = sec(a) [5]
    A'O = sec(b) [5]

  • planar law of cosines on triangle A'OB' along with [4] and [5] gives:
    c'Β² = secΒ²(a) + secΒ²(b) - 2sec(a)sec(b)cos(c) [6]

  • equate [3] and [6]:
    tanΒ²(a) + tanΒ²(b) - 2tan(a)tan(b)cos(C) = secΒ²(a) + secΒ²(b) - 2sec(a)sec(b)cos(c)
    cos(c) = tanΒ²(a) + tanΒ²(b) - 2tan(a)tan(b)cos(C) - secΒ²(a) - secΒ²(b) / -2sec(a)sec(b) [7]

  • apply the trig identity tanΒ²(x) - secΒ²(x) = -1 and obtain:
    cos(c) = -1 - 1 - 2tan(a)tan(b)cos(C) / -2sec(a)sec(b)
    = 2 + 2tan(a)tan(b)cos(C) / 2sec(a)sec(b)
    = 1 + tan(a)tan(b)cos(C) / sec(a)sec(b)
    = 1/sec(a)sec(b) + tan(a)tan(b)cos(C) / sec(a)sec(b)

  • apply trig identities 1/sec(x) = cos(x) and tan(x) = sin(x)/cos(x) and obtain:
    cos(c) = cos(a)cos(b) + sin(a)sin(b)cos(C) [8]

  • [8] is the spherical law of cosines. QED.

#

wasnt actually too difficult, only took like 10 minutes

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it was quite fun seeing it all come together

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esp cuz it was much much shorter than what i had imagined it to be

faint pasture
north kindle
#

I know

faint pasture
faint pasture
#

XD yeaa

twin spindle
#

Tips on proving trig identites? I jus started learning trig, and im stuck on ways to figure out how to prove the identites

cunning lion
#

pick some side, use known identities and algebra until it matches the other side

twin spindle
#

In most scenarios is it typically jus proving, by changing on identity?

faint pasture
faint pasture
# faint pasture

The solution said the area around the corners will bein the form of sector of a circle with radius 3 and central angle 120 degrees
But why do they assume that central angle is gonna be 120? Why not smthn else like 90 or smthn

grave pond
#

Have you drawn a diagram?
The immediate surrounding of each vertex of the original triangle spits into:
60Β° - the original triangle
90Β° - one of the rectangular parts of the desired area
90Β° - another rectangular part of the desired area
the rest - circular sector of the desired area

faint pasture
grave pond
#

We agree that all points in this particular rectangle and sector are in the shape you're looking for, right?

faint pasture
#

Yea

grave pond
#

And obviously the radius as well as the width of the rectangle both have to be 3.

faint pasture
#

Yep thats true

grave pond
#

So the point where the the straight part of the outer perimeter turns into a circular arc is both on the distance-3 parallel, and exactly 3 units from the vertex of the triangle.

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(It would really help to have a diagram to refer to here).

faint pasture
faint pasture
flint ingot
#

Are there any special properties for golden shapes apart from the long side divide short side is golden ratio? For example in 30,60,90 degree triangles the hypotenuse is double the length of the shorter side

grave pond
#

"Golden" is not really a technical term in and of itself.

flint ingot
#

ok

#

then iscosles triangle withh 36,72,72 degree angles

deft sail
flint ingot
#

@deft sail draw a line from the bottom right angle to the side with length 5 which is perpendicular to that side

faint pasture
deft sail
#

I just need to know how to solve it

faint pasture
somber coyoteBOT
#

Sine
Compile Error! Click the errors reaction for more information.
(You may edit your message to recompile.)

deft sail
#

I keep getting the wrong answer some how

faint pasture
#

yea, so can you identify what sides should we call, a, b and c for this case

deft sail
#

Ow

faint pasture
#

nvm

#

im dumb

faint pasture
#

you were right

deft sail
#

Everyone makes mistakes

flint ingot
#

@deft sail u dont need law of cosines

faint pasture
#

what are you getting?

flint ingot
#

idk what law of cosines is but i figured it out

faint pasture
flint ingot
#

oh

#

ok

deft sail
#

Wait

flint ingot
#

sry

deft sail
#

How do I find out without it?

flint ingot
#

so

#

if u draw a line from the bottom right angle to the side with lenght 5

#

which is perpendicular to that lenghth 5

deft sail
#

Can you show me. I’m confused?

flint ingot
#

you see you create a 90,60,30 degree triangle

#

ok ill draw it wait

deft sail
#

Ur saying to split the triangle

faint pasture
flint ingot
deft sail
#

I see it

flint ingot
faint pasture
flint ingot
#

oh ok

faint pasture
#

except it has been generalised

#

so we can just use it as a formula

#

congrats for figuring out the proof on your own!

flint ingot
#

thanks

deft sail
#

Am I gonna find the digonal lines lenght?

#

(I don’t know how to spell)

faint pasture
deft sail
#

The 5 will be split up evenly.

faint pasture
deft sail
#

Hmmm

#

The line I’m making I got 3sqrt(5)

#

C is sqrt(78)?

#

Nvm

#

Here’s another…

faint pasture
#

just use the formula

lilac zinc
#

hello their

naive shale
#

can someone help with this questiion

#

dont tell solution

primal jasper
dark sparrow
lime crownBOT
dark sparrow
#

but also that's overcomplicated lol

clear anvil
#

oh wait lol i thought A = area

slender flint
#

use the strategy here

obsidian harness
#

I knew it

#

Math SE

clear anvil
#

Lol

empty yew
#

How to prove the 4th question.
I have got ```latex
$\cos^{6}\theta+\sin^{6}\theta=1-\sin^{2}\theta\cos^{2}\theta$ and
$\frac{4-3(m^{2}-1)^{2}}{4}=1-3\sin^{2}\theta\cos^{2}\theta$(when substituting $m=\sin\theta+\cos\theta$)

somber coyoteBOT
#

KingDanger

empty yew
#

I am confused what to do next

#

Upto this step am I correct?
Anyone help me

#

<@&286206848099549185>

#

And also i got $-\sqrt{2} \le m \le \sqrt{2}$

somber coyoteBOT
#

KingDanger

faint pasture
faint pasture
lime crownBOT
#

Please do not advertise your help channel or thread in other parts of the server. There are many people who need help, so advertising can quickly turn into spam.

hoary totem
#

that was fast

faint pasture
#

did yall check who was it?

#

i definitely need to start looking at names before clicking at a link-

faint pasture
empty yew
#

It's 1-sin^2cos^2

faint pasture
empty yew
#

@faint pasture How could you please explain?

faint pasture
empty yew
#

Yes

#

Should I send my work?(for checking of mistakes)

faint pasture
empty yew
#

One min

faint pasture
#

this should be a minus

empty yew
#

Oh yes

#

Mb

#

Then it will equal

#

It's proven without the condition m^2 <= 2

#

@faint pasture Is the condition no need?

twin spindle
#

How come the SinΒ²x turned to a CosΒ²x?

hoary totem
empty yew
#

It's an identity

faint pasture
empty yew
twin spindle
#

But ion see the identity on here

hoary totem
#

subtract sinΒ²x from both sides

#

what do you get?

empty yew
#

Gone!!! 😁

formal geyser
#

Can anyone help to find x?

dark sparrow
#

it's 1 - sin^2(x) that became cos^2(x)

hoary totem
twin spindle
#

So basically you're able to change the identity to make it equal another identity?

#

I said that so badly but idk how to explain it πŸ’€πŸ’€

empty yew
# formal geyser

@hoary totem Are lines from the centre joining the tangent equal?

grave pond
#

... by the SAS theorem on the horizontal line, the two-ticks lines, and the 20Β° angles the 40Β° angle gets bisected into.

#

Angles CAO and BAO both have a sine of (radius)/|AO|, so they are equal.
Therefore AHO is congruent to AFO by the SAS theorem.
In particular HO = FO.

hoary totem
#

yeah

#

now u can express AHO in terms of x and constants

#

and solve for x

grave pond
#

(Even if we didn't know that AH=AF, we'd still get the same x, but it would need more work).

#

(Hmm, not that much more work, in fact).

hoary totem
#

or i guess that would be the procedure for proving formulae not identites

#

oops

grave pond
#

HOM = HOC and FOM = FOB

formal geyser
grave pond
#

I've shown you two different ones now.

obtuse quiver
#

Gotta simplify this

#

Can anybody help me w this

hoary totem
obtuse quiver
#

Correct one in help

formal geyser
#

Or sine to the power of 7?

hoary totem
upper karma
#

I need someone to help me and explain to me how to solve my trigonometry homework

hard moon
#

okay

autumn pelican
#

What is SinB? I figured it was just B1

hard moon
#

Hint: law of sines

#

oh wait

#

i see you gave the β€œmeasure of angle B”

#

they just want sine of the angle

autumn pelican
#

Oh I see... I was meant to give the radian not the degree :/

hard moon
#

actually they want sin(56.3Β°)

#

because sinB

autumn pelican
#

I think my brain is fried, I for a minute thought that was the radian conversion ecstasy

#

What am I looking at here?

obtuse quiver
crimson thunder
#

how do i solve this

atomic axle
autumn pelican
maiden brook
hard moon
# crimson thunder how do i solve this

One way to do it is to draw triangles AB and CD (like hockey said), then use the inscribed angle theorem, for example, mBDC = 1/2(161Β°). Then you can find m(DEC) (why?). I’ll leave out the rest

maiden brook
#

yes u can also use exterior angles to triangles

#

and that

crimson thunder
#

._.

maiden brook
#

what?

crimson thunder
#

im stupid and forgot my notes whats the inscribed angle theorem

hard moon
crimson thunder
#

ooooooooh

maiden brook
maiden brook
crimson thunder
#

wait now my math ain't mathing isn't 1/2 of 161 = 80.5

#

how is the angle 93

maiden brook
#

so why is E the center? does it look like it is

crimson thunder
#

e isn't the center its the point where line BD and line AD intersect

maiden brook
#

yeah so what’s wrong then? The inscribed angle theorem doesn’t talk about the 93 degree angle

crimson thunder
#

;-;

#

how do i find measure of arc AD

maiden brook
#

what is the measure of angle BAC

crimson thunder
#

is it 93?

maiden brook
#

why?

crimson thunder
#

because of coresponding angles?

maiden brook
#

look at my diagram

crimson thunder
#

oh

maiden brook
#

corresponding angles? which sides are parallel

crimson thunder
#

87

maiden brook
#

why?

crimson thunder
#

because of linear pairs

#

WAIT

#

OOPS

maiden brook
#

if things dont even look parallel and u have a good diagram and u have no reason for justifying it then those things very likely aren’t parallel

#

anyway, what is angle BAC?

crimson thunder
#

i can't figure it out

maiden brook
#

what’s the theorem we just talked about?

crimson thunder
#

inscribed angle theorem

maiden brook
#

so …

crimson thunder
#

80.5.....

maiden brook
#

yes

#

finally

#

but good

maiden brook
crimson thunder
#

12.5?

maiden brook
#

Good yes

#

Now what is arc AD?

crimson thunder
#

25

#

25

#

OH

#

THANK YOU SO MUCHHHH

maiden brook
#

yes no problem

#

one more thing though @crimson thunder

#

what is the average of arc AD and arc BC (minor arcs) in terms of their measures

crimson thunder
#

180....

#

wait don't they add to be 180

maiden brook
#

what’s their average?

crimson thunder
#

less than 180?

maiden brook
#

bruh

#

what specifically

crimson thunder
#

im stupid idk

maiden brook
#

hopefully u can do that by this point

#

bruh

maiden brook
crimson thunder
#

no

maiden brook
#

the sum of the numbers divided by the number of numbers

crimson thunder
#

so wouldn't be 90?

maiden brook
#

e.g. the average of 1, 4, 10 is (1 + 4 + 10)/3 = 5

maiden brook
crimson thunder
#

186

maiden brook
#

is 186 = 180

#

?

crimson thunder
#

no

maiden brook
#

180?

maiden brook
#

then what’s their average

crimson thunder
#

93

hard moon
#

oh yeah I forgot about that one

maiden brook
crimson thunder
#

it was the original number

hard moon
#

so our problem (with 93Β° angle and 161Β° arc) is just like this one, the difference is instead of given two arcs and we need to find the angle, we are given one angle and one arc and we need to find the other arc

crimson thunder
maiden brook
# crimson thunder how do i solve this

it turns out whenever u have intersecting chords like this the angle between the chords is the average of the two arcs it subtends (the other arc is separated by a (congruent) vertical angle)

crimson thunder
#

i understand how to solve it more simply

maiden brook
#

wdym?

crimson thunder
#

isn't 93 = 1/2(161 + x)

hard moon
#

that’s exactly it

maiden brook
crimson thunder
#

so multiply 2 on both sides and then you subtract 161 from both sides to get 25...

maiden brook
crimson thunder
#

oh

maiden brook
crimson thunder
#

where does what come from

maiden brook
#

do u understand how to derive it?

maiden brook
crimson thunder
#

i understand how to solve it

#

and it came from my notes that i forgot to bring home with me.....

maiden brook
#

if u don’t understand the formula but know how to solve it the way I showed or a similar way, that’s much better

#

it’s not great if u don’t know how to derive it

crimson thunder
#

now i know that the angle comes from the average of the 2 arcs (big one - little one / 2)

#

so thank you

maiden brook
#

that’s not the point

crimson thunder
#

._.

maiden brook
#

it solves it faster but if u had a harder problem where u WERENT given the formula before and it was on an exam, what would u do?

#

and no, it would not be trivialized by a formula like this

#

sorry if I sound like this but it is actually very very helpful to understand how to prove things urself

#

I used to not understand this but for harder problems/some actual problem solving u rlly need this

crimson thunder
maiden brook
#

that’s not good

#

schools fault most likely though

crimson thunder
#

uh oh

maiden brook
#

what?

crimson thunder
#

i did something wrong if you said that's not good ._.

maiden brook
#

I don’t think u do but the problem is if u come across a harder problem that can’t be solved with one of ur formulas, what can u do?

#

the solution I showed (which problem isn’t the best one) only relies on basic techniques, not rlly any specific formulas

#

(yes the inscribed angle, but that’s like the most basic theorem relating to angles in circles)

crimson thunder
#

so i do basic stuff

lavish dew
#

quick question; my geometry project is asking to list a sample space for probailities of a name spinner. Do i have to list off of the possible 276 outcomes or just 20 random outcomes

twin spindle
#

Do yk how this person got cos^2/cos^2

hard moon
#

It appears because 1 - sin^2 (ΞΈ) = cos^2 (ΞΈ), because of the trig identity sin^2 (ΞΈ) + cos^2 (ΞΈ) = 1

trail tendon
#

i don't understand that last part

#

1=1

#

what does it mean??

#

πŸ—Ώ

hard moon
#

it seems it might just be scratch work idk

twin spindle
#

Ohh yeaah I get it now

#

Like this right?

hard moon
#

yeah

twin spindle
#

Bruuvv

#

How did I not notice that 😭😭

#

Thank you πŸ™πŸ™

#

For the Pythagorean identites, does it have to be in the order its said to be?

#

So can this equal to 1?

hard moon
#

the Pythagorean identity is β€œsin^2 (ΞΈ) + cos^2 (ΞΈ) = 1”, and we know this is true; any simple algebraic manipulation will also result in an identity that is true, so what I mean is β€œsin^2 (ΞΈ) = 1 - cos^2 (ΞΈ)” is also an identity and so is β€œcos^2 (ΞΈ) = 1 - sin^2 (ΞΈ)”;

As for β€œcos^2 (ΞΈ) - sin^2 (ΞΈ) = 1”, this isn’t an identity (because both sides are not identical!)

We only have the first three β€œPythagorean identities” I mentioned which have sin^2 and cos^2 in them

#

so yeah it’s just first three

twin spindle
#

I see I see

#

And we can manipulate the identites when needed, right?

hard moon
#

yes

twin spindle
#

Mmmm I see

#

Damn that can be confusing at times πŸ’€πŸ’€

hard moon
#

In fact, β€œcos^2 (ΞΈ) - sin^2 (ΞΈ) = 1” is not an identity, but β€œcos^2 (ΞΈ) - sin^2 (ΞΈ) = 1 - 2sin^2 (ΞΈ) is an identity; you get this from subtracting β€œ2sin^2 (ΞΈ)” on both sides of β€œsin^2 (ΞΈ) + cos^2 (ΞΈ) = 1”

twin spindle
#

Oh wrd, yk what problem I'm doing?

hard moon
#

no I don’t

twin spindle
#

Oh

#

Cause that's littrially the next problem that I'm doing rn πŸ’€πŸ’€

#

Which im actually confused

hard moon
#

πŸ’€πŸ’€πŸ’€πŸ’€πŸ’€πŸ’€πŸ’€πŸ’€πŸ’€

twin spindle
#

I'm confused tho, cause im not sure how to use identites w powers

#

And when a sin is being multiplied by 2

#

Or jus any number being multiplies by a trig function

hard moon
#

alright, well I already gave you a big hint, although it’s not the solution: (the identity comes from subtracting β€œ2sin^2 (ΞΈ)” on both sides of β€œsin^2 (ΞΈ) + cos^2 (ΞΈ) = 1”)

To establish that they’re identical, you would ideally want to establish a chain of equalities showing cos^2 (ΞΈ) - sin^2 (ΞΈ) = … = … = … = 1 - 2sin^2 (ΞΈ)

twin spindle
#

Subtracting?

#

But its alrdy neg?

#

Or did you mean add?

hard moon
#

so since we know sin^2 (ΞΈ) + cos^2 (ΞΈ) = 1 is an identity, the equation would remain an identity if we subtracted 2sin^2 (ΞΈ) on both sides

#

because it’s still identically true

twin spindle
#

Oh wait you meant the pytagorean identity

#

I thought you meant the problem itself 😭

hard moon
#

oh

twin spindle
#

Ohhh wait

#

I see what you mean now

#

Bruv when it involves the pytagorean identites, it always confuses me 😭

hard moon
#

that’s on the right track; however ideally, I think what they are looking for is this:

cos^2 (ΞΈ) - sin^2 (ΞΈ)
= (1 - sin^2 (ΞΈ)) - sin^2 (ΞΈ)
= 1 - 2sin^2 (ΞΈ)

Since it’s a chain of equalities showing that they are equal; this is because in the beginning of your work, it looks like you’re assuming they are equal to start, which is what we’re trying to prove

#

it takes time; eventually you’ll have no problem recognizing the pyth identity (with practice)

twin spindle
twin spindle
#

I jus started learning Trig, so it's kinda confusing πŸ’€πŸ’€

hard moon
#

basically if you removed everything on the right hand side of what you have written, you would have exactly what I wrote

you can think of it like we are taking what you wrote, and only modifying one side of the equation so that the left hand side turns into exactly what is on the right hand side

surreal escarp
#

@cunning lion hey i hope im not bothering u but i still dont know what u meant by this? im pretty sure i got the answer anyway but how is the highest/lowest the same as to get exactly the number #help-24 message

trail tendon
#

<= is greater than or equal to btw

#

idk how to write

surreal escarp
#

so for the 2nd one the lowest x would be x<=84 or something???

surreal escarp
trail tendon
#

oops XD

trail tendon
trail tendon
#

its hard to swap chats XD

trail tendon
#

there should be 5 test scores in total

#

oh wait

surreal escarp
#

oh yeaa sorry thats a old pic, rn i have

#

sorry let me get a pic rq

trail tendon
#

unless x was both the tests lol

trail tendon
#

oh alr

surreal escarp
#

but apparently the x might not be the same so i have to do something else not 2x

trail tendon
#

hmm ok

#

x+y

surreal escarp
#

n find them seperately?

trail tendon
#

i mean i think you have to minimize their sum

surreal escarp
#

wdym

trail tendon
#

x+y is the lowest total score right

surreal escarp
#

yea

trail tendon
#

so you want x+y to be the minimum it can be

#

but also x+y >= 164 right

surreal escarp
#

how is x+y 164?

#

oh wait

#

nvm read that wrong

#

hows it great than or equal to 164

trail tendon
#

but its not actually equals

#

its an inequality

#

and its not actually technically 2x

#

(even tho it can be)

#

but its x + y

#

and your variables have to be greater than or equal to 164, but they also have to be the minimum that they can be

surreal escarp
#

so i did 256+x+y>=420 then subtracted 256 on both sides so now i just have x+y>=164

#

so then id just divide that by 2 to get the final two scores as 82 (but the total score is just 164 anyway)

trail tendon
#

but yeh

pearl pecan
#

can anyone help

pearl pecan
#

ik how to find the angles but not the arcs

surreal escarp
maiden brook
#

measure of angle z? wdym measurement z

trail tendon
pearl pecan
maiden brook
trail tendon
pearl pecan
#

integrated quads?

#

yeah

maiden brook
#

integrated quads?

pearl pecan
#

inscriibed

#

inscribed

#

not integrated mb

surreal escarp
# trail tendon you can only find the sum

so im interpreting this as like if its asking for the highest/lowest number of an average, whatever x or y is has to be result to the said average cuz u cant rlly get any higher or lower than what is asked (respectively)?

#

sorry im not that great with explaining math either

pearl pecan
#

maybe ill find the answer one day

trail tendon
#

i'm not sure what you said XD

surreal escarp
#

so like for example question 3 asks for the highest score she can get for the fourth round to have an average of 92,, x is 86 because it results to exactly 92

#

it cant be 85 cuz thats not the highest but not 87 either cuz its a little more than 92?? idk what im even saying at this point lol

#

or in question 4, x+y has to be 164 cuz anyything else wouldnt be the lowest or itd be too low (like beyond the B grade)

#

idk but u helped me get the answers anyway so thank you

#

🫑

inner vapor
oblique hull
#

@vast skiff

lime dune
lime crownBOT
# inner vapor
What step are you on?
1. I don't know where to begin.
2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
quick skiff
#

can angle Ο† inbetween two diagonals of a paralellogram be 90Β°

#

without it being a rhombus

#

for instance if angles in a paralellogram are 60Β° and 120Β°

#

wouldnt the diagonal split them into 30Β° and 60Β° and you would get 4 congurent triangles

#

each with angles 30 60 and 180 - 90 which is 90

#

but is that possible for a parallelogram, for example sides 4 and 9

dark sparrow
quick skiff
#

thats what i thought

#

but don't diagonals split the angles into two congurent angles

#

ΞΈ/2

#

unless i had a brainfart

formal geyser
#

Can anyone help to solve it

#

I have no clue what to begin with

dark sparrow
#

give names to all relevant points, for a start

quick skiff
formal geyser
quick skiff
#

if not you have similar triangles

formal geyser
formal geyser
quick skiff
#

yes

#

but i don't think we're allowed to assume it passes through that half point

formal geyser
#

I got you now

formal geyser
quick skiff
#

use similarity of triangles

#

10 + x / x = 10 / √(10^2 - x^2)

#

$10 + x / x = 10 / sqrt(10^2 - x^2)$

#

ok idk how to use

#

$\frac{10 + x}{x} = \frac{10}{\sqrt{10^2 - x^2}}$

somber coyoteBOT
quick skiff
#

@formal geyser

pseudo yacht
#

Hello everyone just now joined in this server. need trigonometry formulas from basics

dark sparrow
#

ochem tutor & khanacademy

#

look up their videos on trigonometry

past geyser
#

i rapped it in my head

dark sparrow
#

??

past geyser
#

🎡 khan academy look up their vids of trigonometry 🎹

#

it rhymes

dark sparrow
#

it's a very big stretch of a rhyme

past geyser
#

in rap you can always stretch things

#

you can even rhyme "ryan" with "entitled" if you say it well enough

trail tendon
lilac zinc
#

what is the best visualization for math?

past geyser
#

visualization of what

formal geyser
formal geyser
formal geyser
hard moon
# formal geyser

i found a plausible answer, but the work I had was awkward, since I ended up having to β€œsolve” a quartic equation (which I just used a calculator to obtain the solution)

quick skiff
formal geyser
#

But why?

hard moon
formal geyser
hard moon
#

if you call another side length β€œy” you can obtain a system of equations then solve for x and y (but it became strange as it became unreasonable to do so without an electronic device)

formal geyser
#

But

#

I mean it is more reasonable to say that AC/BC = FC/DC

hard moon
#

yes that’s true

#

the reason is because BD is parallel to AF

#

wait

#

actually I thought you said β€œAC/BC = FC/DC”

#

sorry

quick skiff
#

maybe

#

but its just simpler to go with similarity

quick skiff
hard moon
#

it is simpler if you do it with β€œAC/BC = FC/DC”

you still obtain a quartic equation, but yeah I got the same answer either way

quick skiff
#

OH WAIT NO

#

i meant FC

#

@formal geyser

#

$\frac{10 + x}{x} = \frac{\sqrt{(10+x)^2 + 10^2}}{10}$

somber coyoteBOT