Math Final Help?

Question

Given: sinA=-3/5, pi find exact value of:
A) cos(A + B)
B) Sin2A
C) tan(A-B)

Answer 1

sinA = - 3/5, cosA = - 4/5
cosB = 12/13, sinB = - 5/13
A) cos (s + t) = cos s cos t – sin s sin t
cos(A + B) = (- 4/5)(12/13) - (- 3/5)(- 5/13)
cos(A + B) = (- 4*12)/(5*13) - (3*5)/(5*13)
cos(A + B) = - 48/65 - 15/65
cos(A + B) = - 63/65

B) sin 2t = 2 sin t cos t
sin 2A = 2(- 3/5)(- 4/5)
sin 2A = 2(12/25)
sin 2A = 24/25

C) tan(s + t) = (tans + tant)/(1 - tanstan t)
tanA = 3/4, tanB = - 5/12
tan(A + B) = (3/4 - 5/12)/(1 - (3/4)(- 5/12))
tan(A + B) = (9/12 - 5/12)/(1 + 15/48)
tan(A + B) = (4/12)/(33/48)
tan(A + B) = 16/33