# Can someone confirm if this question is written incorrectly?

I have a question asking me to prove if an identity is true... cos2A = (1-tan^2A)/(1+tan^2A)

I have used the cos2A identity, but the closest I have gotten to Is the numerator on the rhs.

I have looked in the back of the textbook, but unfortunately, the answer or the working out is not in there. Can someone please confirm this for me please?
Identity looks correct to me.
Original post by EmilyBur
I have a question asking me to prove if an identity is true... cos2A = (1-tan^2A)/(1+tan^2A)

I have used the cos2A identity, but the closest I have gotten to Is the numerator on the rhs.

I have looked in the back of the textbook, but unfortunately, the answer or the working out is not in there. Can someone please confirm this for me please?

Generally its easier to simplify, so Id start with the right hand side and express in terms of sin and cos and ...
https://www.tuitionmath.com/single-post/2016/12/09/11-tips-to-conquer-trigonometry-proving
Original post by mqb2766
Generally its easier to simplify, so Id start with the right hand side and express in terms of sin and cos and ...
https://www.tuitionmath.com/single-post/2016/12/09/11-tips-to-conquer-trigonometry-proving

Thankyou so much! I rechecked my working out and I made a few silly mistakes. I must've been half awake -_-'