If Sin A + Cos A = sqrt(2) Sin (90 - A) then Cot A = ??
If P=Sin A.Sin B, Q= Sin C.Cos A, R = Sin A.Cos B and S=Cos A.Cos C then 5(P^2+Q^2+R^2+S^2) = ??
What is the range of the values of k such that k Cos A - 3 Sin A = k + 1
has a real solution?