If Sin A=3/5 and cos B= -12/13, find the value of sin(A-B) if Angle A is in Quadrant I and angle B is in Quadrant III.

Answer 1

in QI, sinA=3/5 means cosA = 4/5
in QIII, cosB = -12/13 means sinB = -5/13

sin(A-B) = sinAcosB - cosAsinB = (3/5)(-12/13) - (4/5)(-5/13) = (-36+20)/65 = -16/65