Triginometry Q3 | Mathematics | Page 1

main imp Jan 9, 2025, 4:58 PM

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Help pls

crystal elbowBOT Jan 9, 2025, 4:58 PM

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main imp Help pls

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orchid timber Jan 9, 2025, 4:59 PM

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main imp Help pls

What have you tried?

main imp Jan 9, 2025, 4:59 PM

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Lit nothing I don’t know where to begin

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Q3

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Triginometry Q3

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@orchid timber

orchid timber Jan 9, 2025, 5:01 PM

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No need to ping me, I can see your comments.

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Well, start by expressing the sides of the rectangle.

main imp Jan 9, 2025, 5:01 PM

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My bad

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Alr I’ll name them x

orchid timber Jan 9, 2025, 5:02 PM

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No need to name them.

main imp Jan 9, 2025, 5:02 PM

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What do I do

orchid timber Jan 9, 2025, 5:02 PM

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Just call them using the letters you're given.

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So, AB and BC, for example.

main imp Jan 9, 2025, 5:02 PM

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Oh ok

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What’s next

orchid timber Jan 9, 2025, 5:03 PM

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What did you get?

main imp Jan 9, 2025, 5:03 PM

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That’s all I have

orchid timber Jan 9, 2025, 5:04 PM

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But why did you say "what's next" if you haven't found the sides yet?

main imp Jan 9, 2025, 5:04 PM

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Ohh

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How am I ment to find them tho

orchid timber Jan 9, 2025, 5:05 PM

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Look at the right triangle AOB.

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You know its hypotenuse and one of its acute angles, so how can you find its sides?

main imp Jan 9, 2025, 5:05 PM

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It’s acute angle is theta

orchid timber Jan 9, 2025, 5:06 PM

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Yes.

main imp Jan 9, 2025, 5:06 PM

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So I don’t know it

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Sin(theta)=BA/5

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Does that mean anything

orchid timber Jan 9, 2025, 5:06 PM

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Yeah, nice! So, you can express AB from there.

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And what about the other side?

main imp Jan 9, 2025, 5:07 PM

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Wait wdym express ab from there

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Oh

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Ab is 5sin(theta)

orchid timber Jan 9, 2025, 5:07 PM

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Well, if sin(θ) = AB/5, what is AB?

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Yes.

main imp Jan 9, 2025, 5:07 PM

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Okay now I do that with the rest

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Do I use cosine rule to find the longer side

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Bc and ad

orchid timber Jan 9, 2025, 5:09 PM

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Yes.

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Obviously, the longer side is just twice the length of AO, so we can still use the same triangle.

main imp Jan 9, 2025, 5:10 PM

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Oh

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Ok one sec

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But I can still use cosine rule right?

orchid timber Jan 9, 2025, 5:12 PM

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Cosine rule? Why?

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Juse find cos(θ).

main imp Jan 9, 2025, 5:13 PM

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I know but let’s just say I didn’t know I could do that and I continued with the cosine rule could I

orchid timber Jan 9, 2025, 5:13 PM

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I mean, I don't see how using the cosine theorem is any easier than just finding the cosine of the angle...

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I mean, it's a right triangle, there's no point in using the cosine theorem for it.

main imp Jan 9, 2025, 5:14 PM

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Ima take that as a it’s not possible to use cosine rule

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Ok I’m find cos theta now

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Ok I got AO=BA/Costheta

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Is that right

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?

orchid timber Jan 9, 2025, 5:16 PM

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No.

main imp Jan 9, 2025, 5:16 PM

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Dam

orchid timber Jan 9, 2025, 5:16 PM

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In a right triangle, cosine of an angle is the ratio of the adjacent side to the hypotenuse.

main imp Jan 9, 2025, 5:16 PM

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Oh ye I did tan

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Ok so AO=5cos theta

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Do I double that now

orchid timber Jan 9, 2025, 5:18 PM

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Yes, that way you can find the longer side AD.

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And then finding the perimeter and the area is easy.

main imp Jan 9, 2025, 5:18 PM

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Ok lemme see

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Ima need some help with atea

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Area

orchid timber Jan 9, 2025, 5:20 PM

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Well, what's the area of the rectangle with sides a and b?

main imp Jan 9, 2025, 5:20 PM

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I multiplied the two sides of the rectangle and got 50Sin(theta)Cos(theta)

orchid timber Jan 9, 2025, 5:21 PM

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Right. So, now recall the double angle formula for sine.

main imp Jan 9, 2025, 5:22 PM

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Which one left or right side

orchid timber Jan 9, 2025, 5:22 PM

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Uh, I mean, what do you think...

main imp Jan 9, 2025, 5:22 PM

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I don’t know when to use which I know for this one it’s prob left but can you explain when you would use which one

orchid timber Jan 9, 2025, 5:23 PM

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The double angle formula for sine.

main imp Jan 9, 2025, 5:23 PM

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Ye there’s two

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Omg

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I’m dumb

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I still dont know tho

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All I see is sin2a and sin^2

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I don’t see just sin

orchid timber Jan 9, 2025, 5:25 PM

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The double angle formula for sine is sin(2θ) = 2sin(θ)cos(θ)...

main imp Jan 9, 2025, 5:25 PM

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Ye but I don’t got sin(20) I just got sin(0)

orchid timber Jan 9, 2025, 5:26 PM

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Look at what you got as the area of the rectangle.

main imp Jan 9, 2025, 5:26 PM

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Oh ye

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Sorry

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It’s 50 in front tho not 2

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So what happens then

orchid timber Jan 9, 2025, 5:27 PM

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main imp It’s 50 in front tho not 2

So just factor 2 from 50.

main imp Jan 9, 2025, 5:27 PM

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Wait why do I divide 50 by 3

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2

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Would I not be taking 2 from 50

orchid timber Jan 9, 2025, 5:28 PM

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Well, yes. 50 = 25*2.

main imp Jan 9, 2025, 5:28 PM

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So 25 2sin(0)

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K=25

orchid timber Jan 9, 2025, 5:29 PM

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Yeah, nice!

main imp Jan 9, 2025, 5:29 PM

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Ok don’t go anywhere I’m prob gonna need help with 4

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I hate deriving

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Where do I begin to derive Cos(A-B)

orchid timber Jan 9, 2025, 5:31 PM

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Well, you have cos(A + B) already.

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The only thing different in cos(A - B) is that there's a minus sign in front of B.

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So, take the formula for cos(A + B) and replace B by -B.

main imp Jan 9, 2025, 5:32 PM

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That would get me full marks?

orchid timber Jan 9, 2025, 5:32 PM

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What?

main imp Jan 9, 2025, 5:33 PM

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So I would have cosAcos(-B)-SinASin(-B)

orchid timber Jan 9, 2025, 5:34 PM

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Right. So, just simplify that.

main imp Jan 9, 2025, 5:35 PM

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Using that

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?

orchid timber Jan 9, 2025, 5:35 PM

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Yes. Cosine is even, sine is odd.

main imp Jan 9, 2025, 5:36 PM

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Ok ty

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How am I ment to prove the second part

orchid timber Jan 9, 2025, 5:38 PM

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Recall that sin(t) = cos(t - π/2).

main imp Jan 9, 2025, 5:39 PM

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Would that be in the formula table or do I have to remember that

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I don’t ever remember seeing that

orchid timber Jan 9, 2025, 5:40 PM

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Then you should review formulas involving trigomometric functions.

main imp Jan 9, 2025, 5:42 PM

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Where’s that

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One of those chapters in trig2?

orchid timber Jan 9, 2025, 5:43 PM

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Yes.

main imp Jan 9, 2025, 5:43 PM

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Which one

orchid timber Jan 9, 2025, 5:43 PM

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Uh...

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I'm not going to answer that question.

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If you had this topic before, you should know.

main imp Jan 9, 2025, 5:44 PM

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U can’t expect me to read through every page to find it

orchid timber Jan 9, 2025, 5:44 PM

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If you're having trouble with the formulas, then you should review the whole chapter.

main imp Jan 9, 2025, 5:44 PM

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😐

main imp Jan 9, 2025, 5:45 PM

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orchid timber Recall that sin(t) = cos(t - π/2).

Why are u using t in this

orchid timber Jan 9, 2025, 5:45 PM

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main imp Why are u using t in this

Just the first variable that came to mind, it doesn't matter.

main imp Jan 9, 2025, 5:45 PM

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Is there any other way without that formula

orchid timber Jan 9, 2025, 5:45 PM

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Hm...

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Can't say anything else comes to mind.

main imp Jan 9, 2025, 5:47 PM

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Ig im skipping part2

orchid timber Jan 9, 2025, 5:48 PM

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Why not just review the chapter...

main imp Jan 9, 2025, 5:48 PM

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Effort

orchid timber Jan 9, 2025, 5:48 PM

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You do seem to be having some trouble with the formulas.

main imp Jan 9, 2025, 5:48 PM

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Would take to much time

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If I flick through the chapter should I see that formula

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@orchid timber

orchid timber Jan 9, 2025, 5:50 PM

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Yes. It's one of the basic formulas that connects sine and cosine.

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Again, why not just review the chapter?

main imp Jan 9, 2025, 5:51 PM

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I will now

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Rlly quickly

orchid timber Jan 9, 2025, 5:51 PM

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No need to rush.

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Take your time, maybe do some exercises using the formulas.

main imp Jan 9, 2025, 5:52 PM

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I’ve got to get to question 10 and each question is taking me like 20 min

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I don’t got time

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And I’ve got other homework aswell

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I’m act done with school

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These teachers think I’m Einstein or something

orchid timber Jan 9, 2025, 5:52 PM

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Sorry, nothing I can do about that.

main imp Jan 9, 2025, 5:53 PM

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Judging based of the work I have to do what year of school do you think I’m in

orchid timber Jan 9, 2025, 5:55 PM

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In my experience here, I've come to notice two things about schools in different countries:

Different amounts of grades in school.
Different programs and order of subjects.
So, I can't reliably answer that.

main imp Jan 9, 2025, 5:55 PM

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Ok what age do you think this work is set for

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A range

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Or an exact

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I’m in Ireland

orchid timber Jan 9, 2025, 5:56 PM

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Again, I don't know. Besides, I graduated high school a while ago, so I don't remember what I had in each grade.

main imp Jan 9, 2025, 5:57 PM

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Ok what is the minimum age do you think this work is suitable for

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By the way I’ll do all the other questions over the weekend

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So thanks for the help

orchid timber Jan 9, 2025, 5:57 PM

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Hm...
Well, trigonometry was in grade 8-9 or so, so I'd say 14-15 or so.

main imp Jan 9, 2025, 5:59 PM

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Using grades which we don’t use in Ireland I’m in grade 11😐

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U must be a genius

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Or something

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Is college better than school bc I act can’t wait to get out of here

orchid timber Jan 9, 2025, 6:00 PM

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I haven't been to college. I went to university after school.

main imp Jan 9, 2025, 6:00 PM

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Same thing no?

orchid timber Jan 9, 2025, 6:01 PM

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No.

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In my case, you can go to college after grade 9, but you can only go to university after grade 11.

main imp Jan 9, 2025, 6:02 PM

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Grade 9

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What

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That 14 yrs old

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15

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What country is this

orchid timber Jan 9, 2025, 6:02 PM

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Yes.

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Russia.

main imp Jan 9, 2025, 6:02 PM

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Holy shit the expectations there must be crazy

orchid timber Jan 9, 2025, 6:03 PM

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Eh, depends on where you want to go.

main imp Jan 9, 2025, 6:03 PM

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Ok anyways thank you bye

orchid timber Jan 9, 2025, 6:03 PM

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You're welcome!

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Make sure to practice.

uncut haloBOT Jan 10, 2025, 7:00 PM

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@main imp

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#Triginometry Q3