Question

Prove the following functions:

(sinx+sin2x)/(1+cosx+cos2x)=tan x
(cos3x/sinx)+(sin3x/cosx)=2cot2x
tan2x=(2/cotx-tanx)

theses are due in the am. Fastness would be great?

Answer 1

You can't prove a function. You can prove an identity.

Using s for sinx, c for cosx, t for tanx, to make things look less cumbersome:

(s+2sc)/(1+c+2c^2 - 1) = t
(s+2sc)/(c + 2c^2) = t
s(1+2c)/[c(1+2c)] = t
s/c = t
t = t

Answer 2

tanx