Hi, can someone please teach me how to solve this?

Question

Find the exact value of the trigonometric expression
cos(89)sin(29)+sin(89)sin(29)

Answer 1

recall that

cos(a-b) = cos(a)cos(b) + sin(a)sin(b)

So, after fixing your typo, you have cos(89-29) = cos(60) = 1/2

Answer 2

Thank You Steve. I now understand it :)