Friday

December 19, 2014

December 19, 2014

Posted by **Ada Enugu** on Tuesday, January 29, 2013 at 1:07am.

1, Cos(A+B)

2, Sin(A+B)

3, Sin(A-B)

- Math -
**Henry**, Thursday, January 31, 2013 at 3:36pmsinA = 8/17 = Y/r.

X^2 + Y^2 = r^2

X^2 + 8^2 = (17)^2

X^2 = (17)^2 - 8^2 = 225

X = 15.

cosA = X/r = 15/17.

cosB = 3/5 = X/r.

X^2 + Y^2 = r^2.

3^2 + Y^2 = 5^2

Y^2 = 5^2 - 3^2 = 16

Y = 4.

sinB = Y/r = 4/5.

1. cos(A+B) = cosA*cosB - sinA*sinB.

cos(A+B) = 15/17 * 3/5 - 8/17 * 4/5 =

45/85 - 32/85 = 13/85.

2. sin(A+B) = sinA*cosB + cosA*sinB.

The student can solve #2, and #3.

**Answer this Question**

**Related Questions**

math - find all solutions in the interval [0,2 pi) sin(x+(3.14/3) + sin(x- 3.14/...

Math - If A and B are acute angle such that SinA=8/17 and CosB=3/5.Find 1, Cos(A...

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

Trig - Please help with this one. I've worked it out in so many ways and can't ...

Math - In any angle ABC prove tht the perimeter = a/Sin A(Sin A + Sin B + Sin C...

tigonometry - expres the following as sums and differences of sines or cosines ...

trig - Reduce the following to the sine or cosine of one angle: (i) sin145*cos75...

Mathematics - Trigonometric Identities - Let y represent theta Prove: 1 + 1/tan^...

algebra - Can someone please help me do this problem? That would be great! ...

Pre-Calculus - How can the following two identities be verified? 1. (cos^2y)/(1-...