<PRE><B>Question 955044</B>
{{{sin(A+B)=sin(A)cos(B)+cos(A)sin(B)}}}
.
.
.
{{{sin(A)=-3/5}}}
{{{sin^2(A)+cos^2(A)=1}}}
{{{9/25+cos^2(A)=1}}}
{{{cos^2(A)=16/25}}}
{{{cos(A)=4/5}}}
.
.
.
{{{cos(B)=3/5}}}
{{{sin^2(B)+cos^2(B)=1}}}
{{{sin^2(B)+9/25=1}}}
{{{sin^2(B)=16/25}}}
{{{sin(B)=-4/5}}}
.
.
.
So then,
{{{sin(A+B)=(-3/5)(3/5)+(4/5)(-4/5)}}}
{{{sin(A+B)=-9/25-16/25}}}
{{{sin(A+B)=-1}}}</PRE>