Let $\mathrm{P}$ be an interior point of a triangle $\mathrm{ABC}$. Let $\mathrm{Q}$ and $\mathrm{R}$ be the reflections of $\mathrm{P}$ in $\mathrm{AB}$ and $\mathrm{AC}$, respectively. IF $\mathrm{Q}, \mathrm{A}, \mathrm{R}$ are collinear then $\angle A$ equals.

• A

  $30^{\circ}$
• B

  $60^{\circ}$
• Correct answer
  C

  $90^{\circ}$
• D

  $120^{\circ}$

Solution

So from Diagram $$ \begin{array}{l} \theta+\theta+\phi+\phi=180^{\circ} \\ \angle \mathrm{A}=\theta+\phi=90^{\circ} \end{array} $$

Hence, the correct answer is option: 'C'.