Find the exact value of each expression, if it is defined. Express your answer in radians.

(a) ( sin⁻¹(-2/2) )
(b) ( cos⁻¹(-2/2) )

a) (a) ( -π/4 ), (b) ( π/4 )
b) (a) ( π/4 ), (b) ( -π/4 )
c) (a) ( -π/2 ), (b) ( π/2 )
d) (a) ( π/2 ), (b) ( -π/2 )