Question

which of the following is not equal to cos(-576)
A.cos 216
B. -cos(-36)
C. sin 126
d. -sin 54
e. cos 144

Answer 1

ANSWER

C. sin 126°

EXPLANATION

-576° is coterminal with ±216,±144.

Therefore

cos (-576°)=cos(±216°)=cos(±144°)

The principal angle for -576° is 36° .

Since the terminal side of -576° is in the second quadrant and the cosine ratio is negative in the second quadrant,

cos (-576°)=-cos (±36°)

Also from complementary angles

cos (-576°)=-cos (36°)=-sin (90-36)=-sin(54°)