Question

Which of the following functions is equal to sin(90° - )?
A. cot(90° - )
B.
csc()
C.
csc(90° - )
D.
cos()

Answer 1

Let sin(90° - )------------------------ > sin (90-x)

sin(a - b) = sin a*cos b - cos a*sin b
so
sin(90 - x) = sin 90*cos x - cos 90 * sin x
sin(90 - x) = 1*cos x - 0* sin x-------- > cos x

 the answer is the option D. cos()