If \(P(0,7,10), Q(-1,6,6)\) and \(R(-4,9,6)\) are three points in the space, then \(P Q R\) is

If \(P(0,7,10), Q(-1,6,6)\) and \(R(-4,9,6)\) are three points in the space, then \(P Q R\) is
  1. right angled isosceles triangle
  2. equilateral triangle
  3. isosceles but not right angled triangle
  4. scalene triangle

Solution

Given points \(P(0,7,10), Q(-1,6,6)\) and \(R(-4,9,6)\) \(\begin{aligned} & \therefore P Q=\sqrt{1+1+16}=\sqrt{18}=3 \sqrt{2} \\ & Q R=\sqrt{9+9+0}=\sqrt{18}=3 \sqrt{2} \\ & \text { and } P R=\sqrt{16+4+16}=\sqrt{36}=6 \\ & \because P Q^2+Q R^2=18+18=36=P R^2 \text { and } P Q=Q R \end{aligned}\) \(\therefore P Q R\) is a right angled isosceles triangle. Hence, option (1) is correct.

Asked in: AP EAMCET 2019 (20 Apr Shift 1)

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