Question 929785
Identity: sin(x+y)=sinxcosy+cosxsiny
{{{sin(3pi/5)cos(7pi/30)+cos(3pi/5)sin(7pi/30)=sin(3pi/5+7pi/30)
=sin(18pi/30+7pi/30)=sin(25pi/30)=sin(5pi/6)=1/2}}}