Question

Which of the following is NOT equal to sin pi/3

A) sin 2pi/3
B) cos pi/6
C) cos 11pi/6
D) sin 4pi/3

Answer 1

D)
`sin((4\pi )/(3) ) = sin(\pi +(\pi )/(3) ) = -sin(\pi )/(3)`

Explanation:

A)

`sin((2\pi )/(3) ) = sin ( \pi - (\pi )/(3) ) = sin(\pi )/(3)`

B)

`cos ((\pi )/(6) ) = cos ( (\pi )/(2) - (\pi )/(3) ) = sin((\pi )/(3))`

C)

`cos ((11\pi )/(6) ) = cos ( (3\pi )/(2) + (\pi )/(3) ) = sin((\pi )/(3))`

D)

`sin((4\pi )/(3) ) = sin(\pi +(\pi )/(3) ) = -sin(\pi )/(3)`