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

Question

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

zepdrix · Answer

$$\Large\rm \sin^2\theta-\cos^2\theta=-1$$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 :[

myininaya · Answer

or recall sin^2(theta)+cos^2(theta)=1

then add the two equations/ together

myininaya · Answer

oops 25 days old
my bad...

zepdrix · Answer

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

myininaya · Answer

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