Question

please help

Answer 1

Please look up the "sum rule for the sine function:" sin (a + b) = ?

Then apply this rule to the problem at hand.

Answer 2

sin(α + β) = sinα cos β + cos α sin β.
cos(α + β) = cosα cos β - sin α sin β.

Answer 3

now what @mathmale

Answer 4

@zepdrix @agent0smith

Answer 5

You wrote out the rule... and then you didn't even use it.