WAEC Mathematics 2015 Paper

Concept:Use the tangent ratio of the required angle in the right triangle formed inside the square.Explanation:Let the side of the square be $1$ unit.In the right triangle containing the marked angle, the side opposite the angle is the full side of the square, so its length is $1$.The adjacent side is half of the square's side, so its length is $\frac{1}{2}=0.5$.Thus, $\tan \alpha = \frac{\text{opposite}}{\text{adjacent}} = \frac{1}{0.5}=2$.So $\alpha = \tan^{-1}(2)$.Using a calculator, $\alpha = 63.43^\circ$.Rounded to the nearest degree, $\alpha = 63^\circ$.Answer:C. $63^\circ$.