Find the exact value of the expression Sin245 degree cos 5 d

Solution

sin(a)cos(b) -cos(a)sin(b)=sin(a-b)

Sin245 degree *cos 5 degree - cos 245 degree * sin 5 degree =sin(245-5)

=sin240 degree

=sin(180+60) degree

=-sin60 degree

=-(3)/2