# trig

posted by .

can you help me find cos 2x if sin x = -12/13 (x in 3rd quadrant)

• trig -

GIVEN: SinX = -12 / 13
SinX = 12/13 = 0.9231, X=67.38(1st.quad.), X = 67.38 + 180 = 247.38
2X = 2*247.34 = 494.76
COS2X = COS 494.76 = -0.7041

## Similar Questions

1. ### TRIG!

Posted by hayden on Monday, February 23, 2009 at 4:05pm. sin^6 x + cos^6 x=1 - (3/4)sin^2 2x work on one side only! Responses Trig please help! - Reiny, Monday, February 23, 2009 at 4:27pm LS looks like the sum of cubes sin^6 x + cos^6 …
2. ### Alg2/Trig

Find the exact value of the trigonometric function given that sin u = 5/13 and cos v = -3/5. (Both u and v are in Quadrant II.) Find csc(u-v). First of all, I drew the triangles of u and v. Also, I know the formula of sin(u-v) is sin …
3. ### trig

can someone please help me with this problem. i'm doing my review right now and i'm stuck?
4. ### 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?
5. ### Trig

find sin(s+t), given that sin t=1/3, t in quadrant 2, and cos s = -2/5, s in quadrant 3
6. ### mth, trig

Given cos a=-7/25 in quadrant II , and sin b=-12/13, in quadrant IV , find cos(a+b) and sin2a
7. ### Trig

Find sin(s+t) and (s-t) if cos(s)= 1/5 and sin(t) = 3/5 and s and t are in quadrant 1. =Sin(s)cos(t) + Cos(s)Sin(t) =Sin(1/5)Cos(3/5) + Cos(-1/5)Sin(3/5) = 0.389418 Sin(s-t) =sin(s)cos(t) - cos(s)sin(t) =sin(-3/5)cos(1/5) - cos(1/5)sin(3/5) …
8. ### Trig

Find sin(x+y), cos(x-y), tan(x+y), and the quadrant of (x+y) if sinx= -1/4, cosy= -4/5, with x and y in quadrant 3.
9. ### Trig

1. Given Sin(A) = ⅗ and Cos(B) = 8/17 in Quadrant I, find Sin(A+B). a) 24/80 [b)] 84/85 c) 60/80 d) 60/85 Find Cos(A+B). a) 32/80 b) -45/85 c) -13/80 [d)] -13/85 Find Tan(A+B) a) 0.8 [b)] -1.72 c) -4.21 d) -6.46 I keep getting …
10. ### Trig

Given Tan(A) = 5 in Quadrant III and Sin(B) = ⅔ in Quadrant II, find Cos(A-B).

More Similar Questions