Posted by **Priya** on Thursday, May 1, 2008 at 2:11pm.

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

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?

- trig -
**Reiny**, Thursday, May 1, 2008 at 3:55pm
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

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