Use a graphing calculator to make a conjecture as to whether each equation is an identity.
-$$( \sin x + \cos x ) ^ { 2 } = 1$$
A) Identity
B) Not an identity

Question

Quizplus · Accepted Answer

The equation $( \sin x + \cos x ) ^ { 2 } = 1$ simplifies to $\sin^2 x + 2\sin x\cos x + \cos^2 x$, which is not always equal to 1 because the identity $\sin^2 x + \cos^2 x = 1$ does not account for the $2\sin x\cos x$ term. Therefore, the given equation is not an identity.

Use a Graphing Calculator to Make a Conjecture as to Whether