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In the given figure, AB = AC, P, Q and R are mid-points of sides BC, CA and AB respectively, then △ PQR is :

In the given figure, AB = AC, P, Q and R are mid-points of sides BC, CA and AB respectively, then △ PQR is : Mid-point Theorem, Concise Mathematics Solutions ICSE Class 9.
  1. scalene

  2. isosceles

  3. equilateral

  4. obtuse angled

Mid-point Theorem

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Answer

Given,

AB = AC = x (let)

From figure,

AR = RB, BP = PC and AQ = QC.

∴ R, P and Q are mid-points of sides AB, BC and AC respectively.

Join QR.

In the given figure, AB = AC, P, Q and R are mid-points of sides BC, CA and AB respectively, then △ PQR is : Mid-point Theorem, Concise Mathematics Solutions ICSE Class 9.

By mid-point theorem,

The line segment joining the mid-points of any two sides of a triangle is parallel to the third side and is equal to half of it.

∴ PQ = 12AB=x2\dfrac{1}{2}AB = \dfrac{x}{2}, PR = 12AC=x2\dfrac{1}{2}AC = \dfrac{x}{2} and QR = 12BC\dfrac{1}{2}BC.

In △ PQR,

PQ = PR.

∴ △ PQR is an isosceles triangle.

Hence, Option 2 is the correct option.

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