Question

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

sin 57° cos 13° - cos 57° sin 13°

a. cos 70°

b. cos 44°

c. sin 44°

d. sin 70°

Answer 1

Use the formula for sin(a-b). Even if you've forgot what it was, you now know the right answer... ;)

Answer 2

@ZeHanz so it will be an A right?

Answer 3

sin(a-b)=sinacosb-cosasinb,
So sin (57°-13°)=sin 57° cos 13° - cos 57° sin 13°
Also, sin (57°-13°)=sin 44°, so the right answer is c.