The origin is translated to $(1,2)$. The point $(7,5)$ in the old system undergoes the following…

The origin is translated to $(1,2)$. The point $(7,5)$ in the old system undergoes the following transformations successively. I. Moves to the new point under the given translation of origin. II. Translated through 2 units along the negative direction of the new $X$-axis. III. Rotated through an angle $\frac{\pi}{4}$ about the origin of new system in the clockwise direction. The final position of the point $(7,5)$ is
  1. $\left(\frac{9}{\sqrt{2}}, \frac{-1}{\sqrt{2}}\right)$
  2. $\left(\frac{7}{\sqrt{2}}, \frac{1}{\sqrt{2}}\right)$
  3. $\left(\frac{7}{\sqrt{2}}, \frac{-1}{\sqrt{2}}\right)$
  4. $\left(\frac{5}{\sqrt{2}}, \frac{-1}{\sqrt{2}}\right)$

Solution

Under the translation of origin to $(1,2)$ the point $(7,5)$ undergoes to $(7-1,5-2) \equiv(6,3)$ Under the translation through 2 units along the negative direction of the new $x$-axis, the point $(6,3)$ undergoes to $(6-2,3) \equiv(4,3)$ Under the rotation throw an angle $\frac{\pi}{4}$ about the origin of new system in the clockwise direction, the final position of point $(7,5)$ $ \begin{aligned} & =\left(4 \cos \frac{\pi}{4}+3 \sin \frac{\pi}{4},-4 \sin \frac{\pi}{4}+3 \cos \frac{\pi}{4}\right) \\ & =\left(\frac{4}{\sqrt{2}}+\frac{3}{\sqrt{2}},-\frac{4}{\sqrt{2}}+\frac{3}{\sqrt{2}}\right)=\left(\frac{7}{\sqrt{2}},-\frac{1}{\sqrt{2}}\right) \end{aligned} $

Asked in: AP EAMCET 2013

Practice more Straight Lines questions on Aicharya