If the ends of the hypotenuse of a right angled triangle are $(0, a)$ and $(a, 0)$ then the locus of the…

If the ends of the hypotenuse of a right angled triangle are $(0, a)$ and $(a, 0)$ then the locus of the third vertex is
  1. $x^2+y^2-a x-a y=0$
  2. $x^2+y^2-a x+a y=0$
  3. $x^2-y^2-a x-a y=0$
  4. $x^2-y^2+a x-a y=0$

Solution

Let $\triangle A B C$ be a right angled triangle with the ends of hypotenuse $A(0, a)$ and $C(a, 0)$ Let co-ordinates of point $B$ is $B(x, y)$ According to Pythagorous theorem, $ \begin{aligned} & (A C)^2=(A B)^2+(B C)^2 \\ & \begin{aligned} \Rightarrow\left(\sqrt{a^2+a^2}\right)^2=\left(\sqrt{(x-0)^2+(y-a)^2}\right)^2 \end{aligned} \\ & \qquad+\left(\sqrt{(x-a)^2+(y-0)^2}\right) \\ & \Rightarrow 2 a^2=x^2+(y-a)^2+(x-a)^2+y^2 \\ & \Rightarrow x^2+y^2-a x-a y=0 \end{aligned} $

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

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