Problem : Express the following as a product: sin(100) - sin(60).

sin(100) - sin(60) = 2 cos((100 + 60))sin((100 - 60)) = 2 cos(80)sin(20).

Problem : Express the following as a product: cos(35) + cos(10).

cos(35) + cos(10) = 2 cos((35 + 10))cos((35 - 10)) = 2 cos(22.5)cos(12.5).