Find the exact values using reference angles a sin120 b cos2

Find the exact values using reference angles.

a) sin(120°)

b) cos(-2/3)

c) sin(7/4)

d) tan(-30°)

a. sin(120)=sin(90+30)=cos 30=sqrt 3/2

b. cos(-2pi/3)=cos(2pi/3)=cos (pi - pi/3)=-sinpi/3=-1/2

c. sin(7pi/4)=sin(2pi - pi/4)=-1/sqrt2

d. tan(-30)=- tan 30= -1/sqrt3