pre calc
posted by Jennifer on .
Find the exact value of sin(xy) if sinx=3/5 in Quadrant III and cosy=5/13 in Quadrant I.

If sin(x)=3/5 in Q3, then
cos(x)=4/5 (using cos²(x)=1sin²(x))
Similarly,
cos(y)=5/13 in Q1 means sin(y)=12/13
sin(xy)=sin(x)cos(y)cos(x)sin(y)
=3/5*5/13  (4/5)*12/13
=(15+48)/65
=33/65