If 3π4 < α < π, then √2 cot α1sin2α is equal to
√2 cot α1sin2α=√2 cot α+cos ec2α=√1+cot2α+2cotα
|1+cotα|since cot α < -1 when 3π4 < α < π, we have |1+cot α|=−1−cot α
If cos A=45 and cos B=1213,3π2<A,B<2π, find the value of the following
(i) cos(A+b)
(ii) sin(A−B)