Thursday

January 29, 2015

January 29, 2015

Posted by **Steve** on Wednesday, December 16, 2009 at 10:06pm.

- trig -
**Reiny**, Wednesday, December 16, 2009 at 10:20pmI am going to use

cos 2A = 1 - 2sin^2 A

or

cos è = 1 - 2sin^2 (è/2)

so we first have to know cos è

make a diagram using sin è = 1/4

then cos è = √15/4

back in our equation...

√15/4 = 1 - 2sin^2 (è/2)

which solves to √[(4-√15)/8]

(I tested my answer on a calculator)

**Answer this Question**

**Related Questions**

trig - how do you work find sin (a-B)beta sign. sin a = 12/13,a lies in quadrant...

Pre-calc/Trig - If cot(a)=3 and sin(b)= (15/17) where a being alpha lies in ...

trig - Find sin è/2 for sin è = - 3/5 and è lies in Quadrant IV

Trig - Find cos(s+t) if cos s= -1/2 and sin t= 3/5, s and t are in quadrant II. ...

Trig - How do i set this trig problem up? PLEASE help me. Find tan (s + t) given...

math - sin a=3/5, a lies on quadrant 1 and sin b=5/13, b lies on quadrant 2. ...

trig - find the 5 trig ratios when sin theta = -5/13 and lies in quadrant 3

TRIG! - Posted by hayden on Monday, February 23, 2009 at 4:05pm. sin^6 x + cos^6...

trig - Find sin è/2 for cos è = 1/4 and è lies in Quadrant I.

trig - If a and b are the measures of two first quadrant angles and sin a = and ...