Question

sin^2 theta - cos^2 theta = -1
i know the answer is pi over 4, but how do i get there?

Answer 1

\[\Large\rm \sin^2\theta-\cos^2\theta=-1\]Multiply both sides by -1,\[\Large\rm \cos^2\theta-\sin^2\theta=1\]Applying Cosine Double Angle Formula,\[\Large\rm \cos2\theta=1\]Leading to,\[\Large\rm 2\theta=0+2k \pi\]Divide by 2 to finish it up.
Hmm the answer is not pi/4, I'm not sure where you got that from :[

Answer 2

or recall sin^2(theta)+cos^2(theta)=1

then add the two equations/ together

Answer 3

oops 25 days old
my bad...

Answer 4

Haha!
Did it pop up on the list somehow? :)

Answer 5

It was high up there I think. I don't think I did too much scrolling. :p