Which is equivalent to sin^-1(0) give your answer in radians.

Express the following as a function of a single angle. cos(60) cos(-20) - sin(60) sin(-20)

1) in triangle the, what is the measure of angle t (in degrees)? 2) in triangle bat, the measure of angle b is 66∘, and the measure of angle t is 77∘.what is the measure of the exterior angle at a (in degrees)?

Can some one me with these questions