Question

(cos²28° − sin²62°) = ?
(a) 0
(b) 1
(c) 2
(d) None of these

Answer 1

$$\begin{gathered} (a)\; 0 \\ \text{We have:} \\ ({\cos }^2{28}^0-{\sin }^2{62}^0) \\ =[{\cos }^2({90}^0-{62}^0)-{\sin }^2{62}^0] \\ =({\sin }^2{62}^0-{\sin }^2{62}^0)[\because \cos ({90}^0-\theta )=\sin \theta ] \\ =0 \end{gathered}$$