Posted by **Anonymous** on Thursday, January 20, 2011 at 2:55am.

cos A = -4/5 for angle A in Quadrant II, find sin 2A

- trig -
**Henry**, Friday, January 21, 2011 at 7:13pm
cosA = -4/5 = -0.80,

A = 143.1deg.

sin(2A) = 2*sinA*cosA,

sin2A = 2*sin(143.1)*cos(143.1 =

-0.9603.

- trig -
**Henry**, Friday, January 21, 2011 at 7:38pm
Solution using Exact values.

cosA = -4/5 = x/r.

(-4)^2 + Y^2 = 5^2,

16 + Y^2 = 25,

Y^2 = 25 - 16 = 9,

Y = 3.

SinA = Y/r = 3/5.

sin2A = 2 * 3/5 * -4/5 = -24/25.

## Answer This Question

## Related Questions

- TRIG! - Posted by hayden on Monday, February 23, 2009 at 4:05pm. sin^6 x + cos^6...
- Trig - Find sin(s+t) and (s-t) if cos(s)= 1/5 and sin(t) = 3/5 and s and t are ...
- Trig - Find cos(s+t) if cos s= -1/2 and sin t= 3/5, s and t are in quadrant II. ...
- trig - Reduce the following to the sine or cosine of one angle: (i) sin145*cos75...
- trig - cos A = -4/5 for angle A in Quadrant II, find sin 2A
- trig - what angle in degrees am i if the following is true: sin t > cos t if ...
- trig - can someone please help me with this problem. i'm doing my review right ...
- mth, trig - Given cos a=-7/25 in quadrant II , and sin b=-12/13, in quadrant IV...
- precalculus - find the values of the requested trig functions using the given ...
- Trig - find sin(s+t), given that sin t=1/3, t in quadrant 2, and cos s = -2/5, s...

More Related Questions