# Math Analysis

posted by .

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

==> I got ã(4-ã7)/2. Is this correct?

• Math Analysis -

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 -

Oops, yeah those were supposed to be radicals :) thanks so much!!!!

## Similar Questions

1. ### simple trig

If sin(theta)=[sqrt(70)]/7 and theta is in Quadrant two, find the exact numerical value of tan theta without using a calculator. I got tan(theta)=[sqrt(294)]/42 Is that right?
2. ### easy trig

If sin(theta)=[sqrt(70)]/7 and theta is in Quadrant two, find the exact numerical value of tan theta without using a calculator. I got tan(theta)=[sqrt(294)]/42 Is that right?
3. ### Math

If sin(x) = /45 and cos(y) = 5/13 with both x and y terminating in quadrant 1 find the exact value of cos(x-y) cos(4/5 - 5/13) Is this what I would do?
4. ### math

If sin(x) = /45 and cos(y) = 5/13 with both x and y terminating in quadrant 1 find the exact value of cos(x-y) cos(4/5 - 5/13) Is this what I would do?
5. ### Math

If sin(x) = 4/5 and cos(y) = 5/13 with both x and y terminating in quadrant 1 find the exact value of cos(x-y) I know that the denominator will be 65
6. ### Trig

Find cos(s+t) if cos s= -1/2 and sin t= 3/5, s and t are in quadrant II. I got the answer to be -4/10 plus -3sqrt(3)/10. Is that right?
7. ### Math Analysis

Use the half-angle formula to find the exact value of cos(x/2) when tanx = -5/8 and x is in quadrant IV. (| is a radical) ==> I got sqrt((89 + 8sqrt(89))/178). Is this correct?
8. ### Trig hep, please? Thank you!

1. Find the exact value of sin(195(degrees)) 2. If cot2(delta)=5/12 with 0(<or =)2(delta)pi, find cos(delta), sin(delta) , tan(delta). 3.find the exact value of sin2(x) if cos(x)= 4/5. (X is in quadrant 1) 4. Find the exact value …
9. ### Math

Find the exact value of the trig expression given that sin u = -5/13 and cos v = -4/5. u and v are in the second quadrant. cos(v - u)
10. ### Trigonometry

Suppose *u* is a quadrant IV angle with cos(u) = 3/5. Suppose *v* is a quadrant IV angle with cos(v) = 12/13. Find the exact value of sin(u-v) I have gotten to sin120cos150 - sin150cos120 but I am not sure I am correct up to that point …

More Similar Questions