(a) If sinA=1213 and sinB=45, where π2<A<π and 0<B<π2, find the following: (i) sin(A+B) (ii) cos(A+B) (b) If sinA= 35, cosB=1213, where A and B both lie in second quadrant, find the value of sin(A+B).
If sin A = 45 and cos B = - 1213, where A and b lie in first
and third quadrant respectively, then cos(A + B) =