Can someone help with these two answers ill give more points

Atriangle with all sides of equal length is a/an triangle. a. right b. scalene c. equilateral d. isosceles

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)?