If the polar co-ordinates of a point are $\left(\sqrt{2}, \frac{\pi}{4}\right)$, then its Cartesian…

If the polar co-ordinates of a point are $\left(\sqrt{2}, \frac{\pi}{4}\right)$, then its Cartesian co-ordinates are
  1. $(\sqrt{2}, 2)$
  2. $(1,-1)$
  3. $(2, \sqrt{2})$
  4. $(1,1)$

Solution

Polar coordinates $\mathrm{z}=\mathrm{a}+\mathrm{ib}$ are $\left(\sqrt{2}, \frac{\pi}{4}\right)$ $\therefore \sqrt{2}=\sqrt{\mathrm{a}^2+\mathrm{b}^2} \Rightarrow \mathrm{a}^2+\mathrm{b}^2=2$ and $\tan \left(\frac{\pi}{4}\right)=\frac{\mathrm{b}}{\mathrm{a}} \Rightarrow \frac{\mathrm{b}}{\mathrm{a}}=1$ $\Rightarrow \mathrm{a}=\mathrm{b}$ $\therefore \mathrm{a}^2+\mathrm{b}^2=2 \Rightarrow 2 \mathrm{a}^2=2 \Rightarrow \mathrm{a}^2=1 \Rightarrow \mathrm{a}= \pm 1$ Since point lies in $1^{\text {st }}$ quadrant, $a=1 \Rightarrow b=1$ $\therefore$ Cartesian coordinates are $(1,1)$

Asked in: MHT CET 2021 (21 Sep Shift 1)

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