With usual notations, if the angles $A, B, C$ of a $\triangle A B C$ are in A.P. and $b: c=\sqrt{3}:…

With usual notations, if the angles $A, B, C$ of a $\triangle A B C$ are in A.P. and $b: c=\sqrt{3}: \sqrt{2}$, then $\angle \mathrm{A}=$
  1. $55^{\circ}$
  2. $45^{\circ}$
  3. $35^{\circ}$
  4. $75^{\circ}$

Solution

Since $A, B, C$ are in A.P., $2 B=A+C \Rightarrow B=60^{\circ}$ We know that, $\frac{\sin B}{b}=\frac{\sin C}{c} \Rightarrow \sin C=\frac{C}{b} \times \sin 60^{\circ}$ $\therefore \sin C=\frac{\sqrt{2}}{\sqrt{3}} \times \frac{\sqrt{3}}{2}=\frac{1}{\sqrt{2}}$ $\therefore \quad C=45^{\circ} \Rightarrow A=180^{\circ}-\left(60^{\circ}+45^{\circ}\right)=75^{\circ}$

Asked in: MHT CET 2020 (19 Oct Shift 2)

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