Use a graphing calculator to make a conjecture as to whether each equation is an identity.
-cos(x + y)= cos x + cos y
A)Identity
B)Not an Identity

Question

Quizplus · Accepted Answer

The equation cos(x + y) = cos x + cos y is not an identity because the left side represents the cosine of the sum of two angles, which has a specific formula, cos(x + y) = cos x cos y - sin x sin y, which does not simplify to the right side, cos x + cos y. Graphing both sides of the equation would show different values for most x and y, confirming it's not an identity.

Use a Graphing Calculator to Make a Conjecture as to Whether