Question 1040904
How about this?
{{{sin(x-y)=sin(x)cos(y)-cos(x)sin(y)}}}
So in this case {{{x=B}}} and {{{y=A}}}.
So,
{{{sin(y)=5/13}}}
 and 
{{{cos(y)=12/13}}} or {{{cos(y)=-12/13}}}
and
{{{cos(x)=4/5}}} 
and
{{{sin(x)=3/5}}} or {{{sin(x)=-3/5}}}
Take it from there and complete it.
Don't get hung up on the variables, they're just  placeholders. 
When you run into something like this where it's confusing, just change the variable names and keep your head straight. 
Good luck!