WAEC Mathematics 2021 Paper

Concept:An exterior angle of a regular polygon must divide $360^\circ$ exactly because it equals $\frac{360^\circ}{n}$ for some whole number $n$.Explanation:For a regular polygon with $n$ sides, each exterior angle is given by:$$\text{exterior angle} = \frac{360^\circ}{n}$$Thus, $360^\circ$ must be perfectly divisible by the given angle.Check each option:$360 \div 66 = 5.45$, which is not a whole number.$360 \div 72 = 5$, so $72^\circ$ is possible for a pentagon.$360 \div 24 = 15$, so $24^\circ$ is possible.$360 \div 15 = 24$, so $15^\circ$ is possible.Therefore, $66^\circ$ cannot be an exterior angle of a regular polygon.Answer:A. $66^\circ$