In Exercises 1-4, determine whether the statement is true or false. Justify your answer.
1. sin(u ± v) = sin u cos v ± cos u sin v
2. cos(u ± v) = cos u cos v ± sin u sin v
3. When α and β are supplementary, sin α cos β = cos α sin β.
4. When A, B, and C form ∆ ABC, cos(A + B) = −cos C.