Please help me with these problems.

6-87. Use the angle difference formula for cosine to simplify cos(it - 0) . Write your answer as an identity and check it for 0 = 5. 6-88. Use the angle difference formula for sine to simplify sin(it -0) . Write your answer as an identity, and check it for 0 = 5. 6-89. Solve for x on the indicated domain. a. cos x = 0, [0, 270 ] b. 2 sin x + V2 = 0, [0, 27] C. cos x(2 sin x + v2) = 0, [0, 2x] d. cos x(2 sin x + V2) =0 6-90. Simplify: (csc x + cot x)(1-cos x) 6-91. Simplify : Xy + x 2y y-+x- 2