in triangle ABC p, q, r are the midpoint of sides AB, BC, CA respectively. Prove that the straight lines PQ, QR, RP form four congruent triangle
Answers
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In Δ ABC
P is the midpoint of AB
R is the midpoint of CA
∴ By midpoint theorem,
PR ║ BC
PR = BC
Since Q is the midpoint of BC,
PR = BC
∴ PBQR is a Parallelogram
(One pair of opposite sides are equal (PR = BC) and parallel (PR║BC)
Similarly,
PRCQ is a parallelogram
APQR is a parallelogram
Now,
In Parallelogram PBQR
ΔPBQ ≅ ΔPRQ → 1
(Diagonals of a parallelogram divide it into two congruent triangles)
In Parallelogram PRCQ
ΔPRQ ≅ ΔCRQ → 2
(Diagonals of a parallelogram divide it into two congruent triangles)
In Parallelogram APQR
ΔAPR ≅ ΔQPR → 3
(Diagonals of a parallelogram divide it into two congruent triangles)
Now,
From 1, 2 and 3
ΔPBQ ≅ ΔPRQ ≅ ΔCQR ≅ ΔAPR
Therefore, the linesegments joining the midpoints of the sides of a triangle, form four congruent triangles.
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