prove that converse of Pythagoras theorem.
Answers
Answer:
Converse of the Pythagorean Theorem: If the square of the length of the longest side of a triangle is equal to the sum of the squares of the lengths of the other two sides, then the triangle is a right triangle. Proof: ... By the Pythagorean Theorem, BD² = a² + b² = c², and so BD = c.
Given :
- AC² = AB² + BC²
To prove :
- ABC is a right angled triangle.
Construction : Draw a right angled triangle PQR such that, angle Q = 90°, AB = PQ, BC = QR.
Proof :
In triangle PQR,
Angle Q = 90°
Also,
PR² = PQ² + QR² ( By using Pythagoras theorem )...(1)
AC² = AB² + BC² ( Given )
Also, AB = PQ and BC = QR
Therefore,
AC² = PQ²+ QR²....(2)
From eq (1) and (2),
PR² = AC²
So, PR = AC
Now,
In ∆ABC and ∆PQR,
AB = PQ
BC = QR
AC = PR
Hence,
∆ABC is congruent to ∆PQR by SSS criteria.
Therefore, Angle B = Angle Q ( By CPCT )
_____________________________
Angle Q = 90°
Therefore,
Angle B = 90°
Thus, ABC is a right angled triangle with Angle B = 90°
Hence proved.
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