Posted by Ada Enugu on Tuesday, January 29, 2013 at 1:07am.
If A and B are acute angle such that SinA=8/17 and CosB=3/5.Find
1, Cos(A+B)
2, Sin(A+B)
3, Sin(AB)

Math  Henry, Thursday, January 31, 2013 at 3:36pm
sinA = 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 ...
 tigonometry  expres the following as sums and differences of sines or cosines ...
 math  Given that [sin(AB)/cos(A+B)]=1/3[tan(AB)], find the values of cosB if ...
 trig  Reduce the following to the sine or cosine of one angle: (i) sin145*cos75...
 Math  In any angle ABC prove that the perimeter = a/Sin A(Sin A + Sin B + Sin C...
 Mathematics  Trigonometric Identities  Let y represent theta Prove: 1 + 1/tan^...
 algebra  Can someone please help me do this problem? That would be great! ...
More Related Questions