# Math Help - Trigo qn

1. ## Trigo qn

Please do the last part of the qn "By using the relation sin2x=cos(90-2x), find one of these solutions by calculation."

2. Originally Posted by maybeline9216
Please do the last part of the qn "By using the relation sin2x=cos(90-2x), find one of these solutions by calculation."
we have $\sin 2x = \cos 3x$

then we are told $\sin 2x = \cos(90 - 2x)$

this means that $\cos (90 - 2x) = \cos 3x$

$\Rightarrow 90 - 2x = 3x$

now continue

3. O.o so easy arh?? thanks