What does negative sine squared plus cosine squared equal?

-Sin^(2)(Theta) + Cos^(2)Theta =>

Cos^(2)Theta - Sin^(2)Theta

Factor

(Cos(Theta) - Sin(Theta))( Cos(Theta) + Sin(Theta))

#Is the Pythagorean factors .

Or

-Sin^(2)Theta = -(1 - Cos^(2)Theta) = Cos(2)Theta - 1

Substitute

Cos^(2)Thetqa - 1 + Cos^(2) Theta =

2Cos^(2)Theta - 1