If two angles of $\triangle \mathrm{ABC}$ are $\frac{\pi}{4}$ and $\frac{\pi}{3}$, then the ratio of the…

If two angles of $\triangle \mathrm{ABC}$ are $\frac{\pi}{4}$ and $\frac{\pi}{3}$, then the ratio of the smallest and greatest sides are
  1. $(\sqrt{3}-1): 1$
  2. $\sqrt{3}: \sqrt{5}$
  3. $\sqrt{2}: \sqrt{3}$
  4. $(\sqrt{3}-1): 4$

Solution

Let three angles of the triangle be given as $\mathrm{A}=\frac{\pi}{4}, \mathrm{~B}=\frac{\pi}{3}$ and $\mathrm{C}=\frac{\pi}{4}+\frac{\pi}{6}$ Let a, b, c be the opposite to angles A, B, C respectively. As $\frac{\sin A}{a}=\frac{\sin C}{c}$, we get $\text { Required Ratio }=\frac{\mathrm{a}}{\mathrm{c}}=\frac{\sin \mathrm{A}}{\sin \mathrm{C}}$ $=\frac{\sin \left(\frac{\pi}{4}\right)}{\sin \left(\frac{\pi}{4}+\frac{\pi}{6}\right)}$ $\begin{aligned} & =\frac{\sin \frac{\pi}{4}}{\sin \frac{\pi}{4} \cos \frac{\pi}{6}+\cos \frac{\pi}{4} \sin \frac{\pi}{6}} \\ & =\frac{2}{\sqrt{3}+1} \\ & =\frac{2(\sqrt{3}-1)}{2} \\ & =(\sqrt{3}-1): 1\end{aligned}$

Asked in: MHT CET 2023 (12 May Shift 2)

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