# identities

1. ### Trigonometric identities

hi all Need help on the below, all help appreciated. Find the values from 0 degree to 360degree which satisfy the equation 2siny-5tany = 0 My ans: 2- 5 (tan y/ sin y) = 0 2 cos y - 5 = 0 cos y = 2.5 Ans from textbook is 0,180 & 360 degree. I keep getting 2.5. Appreciate all help.
2. ### Trig Identities

Hello If you guys could help me solve this identity that would be awesome :) sin2x(cotx+1)2=cos2x(tanx+1)2 Thanks (Clapping)
3. ### Trig Identities

Hello Please help me with this question cos(x+y)cos(x-y)=cos2x+cos2y The trick is that the left side is correct so what ever it equals is the right number, but the left side is missing one piece at the end, so in order to complete the question(they are equal to each other) we need to find...
4. ### PLZ help...Trigonometry Identities

I have cos(-x)/ sec(x)+tan(-x). So,here what I did. cos(x)/ (1/cos(x) - (sin(x)/cos(x)) cos(x)/ (1-sin(x)/ cos(x)) cos^2 (x) / (1-sin(x)) <------That's wrong though so where did I go wrong and what's the answer.
5. ### Simple Trigonometric Identities Exercise - Got Stuck

I was just browsing a textbook and try to solve this exercise quoted as follows: I started by thinking in it's full form that is, \frac{\sin \theta }{\cos \theta}=\tan \theta Secondly, I noticed this lacking\cos \theta is to be found using this identity \cos\theta =\sqrt{1-\sin ^{2}\theta...
6. ### Trigonometric identities

How do I solve this question..... I can't think of any way... Plz help!
7. ### Simplifying a derivative with trig functions / identities

Good evening, Directions: Calculate y' if sin(x+y) = y^2 * cos x [0,pi] I'm able to follow the steps to solving and simplifying this all the way to the following: y' = ( -y^2 * sinx - cos(x+y) ) / ( cos(x+y) - 2ycosx ) The next thing that my TA wrote on the board was y' = - (-1) / 1 How do...
8. ### Proofing set identities

Hi i am having serious problems proving this. Can you help me?
9. ### Bombing on a Trig Equations and Identities assignment, could use some help

Hey Everyone, I've really been struggling with a trigonometry assignment so I thought I'd ask for some help, there's about 6 questions out of 20 I'm totally lost on and thought I'd ask on a few and see if it helped me with a 'Eureka' moment and I could get the rest on my own. 1) Write the...
10. ### Inverse function's range and trig identities

Had a question like this whilst revising: Let y = cos(x) Evaluate arccos(y) + arcsin(y) I used the trig identity cos(x) = sin(x + pi/2) and so the answer came to 2x + pi/2. According to the mark scheme that was wrong and the answer involves using the trig identity cos(x) = sin(pi/2 - x) which...
11. ### Trigonometric Identities

Dear all, I have worked out tanAtanB but have trouble finding tan A + tan B (As per my working) Please help. Thanks in advance
12. ### Trig proof problem

Hi, I need to proof the following equation is true, e.g. that the left hand side is equal to the right hand side. (sin2(360 - x) + cos(90 + 2x) + cos2(180 - x)) / (sin(90 - 2x)) = (cosx -sinx) / (cosx + sinx) I only got this and can't go further: (-sin2x-1) / (1 - sin2x) Any help please...
13. ### Trig - Cofunction angle identities

Could someone explain to me how to solve cofunction idetnies. Here are some I didnt understand how to solve sin(3pi/2 -x)= ? cos(3pi/2 -x)= ? sec(3pi/2 -x)= ?
14. ### Trigonometric Identities

Suppose −π/2< x < 0 and sin(x) = −√5/3, and cot(y) = 2√2. Find theexact value of cos(x) + cos(4y). Using cos^2(x)+sin^2(x)=1, I worked out that cos(x)=2/3 but that doesn't seem to satisfy the condition that − π/2 < x < 0. Please help. I have found cos(y) using cot*y)=1/tan(y) and the sec...
15. ### Trigonometric Identities

Need help understanding the question: If sin t=c, 0 < t < pi/2, find in terms of c: (a) sin(pi-t) (b) cos(-t) Do I need to use this type of function?: sin(a-b) = sin(a)cos(b) - cos(a)sin(b) And how would state my answer that it is 0 < t < pi/2 Thanks
16. ### Trigonometric and hyperbolic identities

Hi Im struggling with this question would be greatful for some advice. Thanks Q1. Involves trigonometric identities and an understanding of polar and Cartesian coordinates. Note that Sin and Cos are cyclical, ie. there is more than one angle for each value, so if the first gives an...
17. ### Which of the following equations are identities? Check all that apply.

Which of the following equations are identities? Check all that apply. Please explain. Thank you!
18. ### How to deduce trig identities?

Given that sin2θ + cos2θ = 1, how do you deduce that 1 + cot2θ = csc2θ or tan2θ = sec2θ - 1?
19. ### trig identities question help

Hi, I was wondering if I could have help with the following question.
20. ### Trig Identities

Hi all. I have a question: tanx= -(8/5), where sinx >0 and cosx <0 find sin(2x)? I know that I should start looking to see what trig identities that I could use to help me solve this problem. So I made a right triangle and solved for all three sides using the pythagorean theorem. On the next...