WAEC Mathematics 2016 Paper

Concept:The exterior angle of a triangle equals the sum of the two opposite interior angles. Vertically opposite angles are equal.Explanation:In the diagram, let the angle vertically opposite to $p$ be $\beta$.Vertically opposite angles are equal, so $\beta = p$.The angle $n$ is an exterior angle of the triangle.The exterior angle equals the sum of the two interior opposite angles, $m$ and $\beta$.Thus, $n = m + \beta$.Substitute $\beta = p$ into this equation.Therefore, $n = m + p$.Answer:Option D: $n = m + p$.