The perpendicular distance from the point $(1, \pi)$ to the line joining $\left(1,0^{\circ}\right)$ and…

The perpendicular distance from the point $(1, \pi)$ to the line joining $\left(1,0^{\circ}\right)$ and $\left(1, \frac{\pi}{2}\right)$, (in polar coordinates) is
  1. $2$
  2. $\sqrt{3}$
  3. $1$
  4. $\sqrt{2}$

Solution

Given points $(1, \pi),\left(1,0^{\circ}\right)$ and $\left(1, \frac{\pi}{2}\right)$ are in polar form. Now, change in cartesian form, $ \begin{aligned} & (1, \pi) \rightarrow(1 \cdot \cos \pi, 1 \cdot \sin \pi) \rightarrow(-1,0) \\ & \left(1,0^{\circ}\right) \rightarrow\left(1 \cdot \cos 0^{\circ}, 1 \cdot \sin 0^{\circ}\right) \rightarrow(1,0) \\ & \text { and }\left(1, \frac{\pi}{2}\right) \rightarrow\left(1 \cdot \cos \frac{\pi}{2}, 1 \cdot \sin \frac{\pi}{2}\right) \rightarrow(0,1) \\ & \end{aligned} $ Now, equation of the line passing through $(1,0)$ and $(0,1)$ is $ \begin{aligned} & (y-0)=\frac{1-0}{0-1}(x-1) \\ & \Rightarrow \quad y=-x+1 \\ & \Rightarrow \quad x+y-1=0 \\ & \end{aligned} $ So, the perpendicular distance from the point $(-1,0)$ to the line (i) is $ =\frac{|-1+0-1|}{\sqrt{1+1}}=\frac{2}{\sqrt{2}}=\sqrt{2} $

Asked in: AP EAMCET 2013

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