Posted by **Emily** on Monday, May 3, 2010 at 8:52pm.

Find the exact value of cos(x/2) if sin x = 3/4 and x is in quadrant II.

==> I got (4-7)/2. Is this correct?

- Math Analysis -
**Reiny**, Monday, May 3, 2010 at 9:24pm
I can't read your symbols, but

if sinx = 3/4 in II then

cos x = -√7/4

cosx = 2cos^2 (x/2) - 1

-√7/4 + 1 = 2cos^2 (x/2)

(4-√7)/8 = cos^2 (x/2)

cos x/2 = √[(4-√7)/8]

- Math Analysis -
**Emily**, Monday, May 3, 2010 at 9:27pm
Oops, yeah those were supposed to be radicals :) thanks so much!!!!

## Answer This Question

## Related Questions

- Trig hep, please? Thank you! - 1. Find the exact value of sin(195(degrees)) 2. ...
- Math Analysis - Use the half-angle formula to find the exact value of cos(x/2) ...
- Trigonometry - Suppose *u* is a quadrant IV angle with cos(u) = 3/5. Suppose *v...
- easy trig - If sin(theta)=[sqrt(70)]/7 and theta is in Quadrant two, find the ...
- simple trig - If sin(theta)=[sqrt(70)]/7 and theta is in Quadrant two, find the ...
- math - If sin(x) = /45 and cos(y) = 5/13 with both x and y terminating in ...
- Math - If sin(x) = /45 and cos(y) = 5/13 with both x and y terminating in ...
- Trig - Find cos(s+t) if cos s= -1/2 and sin t= 3/5, s and t are in quadrant II. ...
- Math - If sin(x) = 4/5 and cos(y) = 5/13 with both x and y terminating in ...
- Math - Find the exact value of the trig expression given that sin u = -5/13 and ...

More Related Questions