Question
The difference between the two acute angkes of a right angles triangle is $\frac{2\pi}{5}$ redians. Express the angles in degrees.

Answer

Let $\theta_{1}$ and $\theta_{2}$ be two acute angles of a right angles triangle. $\therefore$ Difference of acute angles. $\theta_{1}-\theta_{2}=\frac{2\pi}{5}\ \text{radians}$ $\therefore$ In a right angled triangle, $\theta_{1}+\theta_{2}=\frac{\pi}{2}$ $\theta_{1}+\theta_{2}=\frac{2\pi}{5}$ $\theta_{1}+\theta_{2}=\frac{\pi}{2}$ On solving $2\theta_{1}=\frac{2\pi}{5}+\frac{\pi}{2}$ $\theta_{1}=\frac{9\pi}{20}$ From quation (ii) $\theta_{2}=\frac{\pi}{20}$ So angles in degrees, $\theta_{1}=\frac{9\pi}{20}\times\frac{180}{\pi}=81^{\circ}$ $\theta_{2}=\frac{\pi}{20}\times\frac{180}{\pi}=9^{\circ}$

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