Prove the identity 9 - sin? (x) - cos(x) = 8 9 - sin? (2) - cos (x) = The left side is more complicated so start there: Group the trigonometric terms together and factor out a negative: Now you have: 1. sin? (x) + cos(r) 2. Use a Pythagorean identity: 9 = Now you have: 9-sin(x) + cos(2) = 3. Subtract: 8 Proven! 8