Question

How do I do this?

Answer 1

Write the expression as the sine, cosine, or tangent of an angle.

cos 94° cos 37° + sin 94° sin 37°

Answer 2

but its adding so would I do sin(a+b)

Answer 3

oh sorry it should be cos of a difference of angles.

Answer 4

\[ \cos(α − β) = \cos α \cos β + \sin α \sin β \]

Answer 5

so the answer would be cos 57°?

Answer 6

Yes. That is the correct answer.

Answer 7

what difference of angles equation would I use if it is in this form: sin cos - cos sin

Answer 8

Look here: http://www.intmath.com/analytic-trigonometry/2-sum-difference-angles.php

Answer 9

oh okay thank you

Answer 10

These formulas are quite hard to remember, but if you know complex numbers it can be easily derived.