If $O$ is the origin and $P, Q$ are points on the line $3 x+4 y+$ $15=0$ such that…

If $O$ is the origin and $P, Q$ are points on the line $3 x+4 y+$ $15=0$ such that $\mathrm{OP}=\mathrm{OQ}=9$, then the area of $\triangle \mathrm{OPQ}$ is
  1. $6 \sqrt{2}$
  2. $9 \sqrt{2}$
  3. $12 \sqrt{2}$
  4. $18 \sqrt{2}$

Solution

Let $M$ be the foot of perpendicular drawn from $O(0,0)$ on line $3 x+4 y+15=0$
Hence $O M=\left|\frac{3 \times 0+4 \times 0+15}{\sqrt{3^2+4^2}}\right|=3$ Now since $\triangle O M Q$, $ M Q=\sqrt{81-9}=6 \sqrt{2} $ Area of $\triangle O P Q=2[$ Area of $\triangle O M Q]$ $ \begin{aligned} & =2\left[\frac{1}{2}(O M)(M Q)\right] \\ & =3 \times 6 \sqrt{2}=18 \sqrt{2} \end{aligned} $

Asked in: AP EAMCET 2023 (19 May Shift 1)

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