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

in QI, sinA=3/5 means cosA = 4/5
in QIII, cosB = 12/13 means sinB = 5/13
sin(AB) = sinAcosB  cosAsinB = (3/5)(12/13)  (4/5)(5/13) = (36+20)/65 = 16/65
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