Question

if sin A=3/5 and cos B=-12/13, A and B obtuse, find: a) sin(A-b) b)cos(A+B)

Answer 1

well you 1st need to find the missing sides in each triangle.. both 2nd quadrant angles



the use

sin(A - B) = sinAcos(B) - cos(A)sin(B)

and substitute the exact values from the triangles.

and for (b)

cos(A + B) = cos(A)cos(B) - sin(A)sin(B)

again substitute and simplify

hope it helps

Answer 2

I'll try it out thank you

Answer 3

I got A.) -16/65, B.) 33/65

Answer 4

A.) sin(3/5)cos(-12/13)-cos(-4/5)sin(5/13)

B.) cos(-4/5)cos(-12/13)-sin(-3/5)sin(5/13)