Question

solve cos^2(x) - sin^2(x) = -1

Answer 1

this is false.

Answer 2

You know that \[Cos^2x+Sin^2x=1\]
Divide both sides by -1.
\[-Cos^2x-Sin^2x=-1\]
See how your equation differs?

Answer 3

In your equation and in the identity, add\[Sin^2x\]to both sides,\[Identity->-Cos^2x=-1+Sin^2x\]\[Your's->Cos^2x=-1+Sin^2x\]

Answer 4

thanks for your help!! thats what i got but i was sure i was doing something wrong, since it was a test question.

Answer 5

Anytime!