Find sin (alpha/2) and cos (alpha/2)

Question

sin alpha = 3, -pi/2 < alpha <less then or equal to 0

How to get the answer of sin (alpha/2) = -1/square root 3, cos(alpha/2) = square root 6/3?

Answer 1

You said "sin alpha = 3"

check your typing, the sine of any angle must be between ±1

Looking at your answers, α/2 is in the fourth quadrant, with x=√2, y=-1, and r=√3