ABC is a right angle triangle at B.If D and E are mid point of BC and AB respectively prove that AD^2+CE^2=5DE^2
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Step-by-step explanation:
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Answer:
Given:
- ABC is a right angled triangle at B.
- D and E are mid point of BC and AB respectively.
To prove:
- AD² + CE² = 5DE²
Solution:
AB = 2BE = 2AE ... since E is midpoint of seg AB.
BC = 2BD = 2CD ... since D is midpoint of seg BC.
AC = 2ED
Reason:
Line formed by joining midpoints of two side of triangle is always parallel to third side and also half of the third side.
In ∆ ABC,
(i) AC² = AB² + BC².... By Pythagoras theorem
In ∆ ABD,
(ii) AD² = AB² + BD²... By Pythagoras theorem
In ∆ EBC,
(iii) CE² = BE² + BC²... By Pythagoras theorem
In ∆ EBD,
(iv) DE² = EB² + BD²
Add equations (ii) and (iii), we get
=> AD² + CE² = AB² + BD² + BE² + BC²
=> AD² +CE² = AB² + BC² + BD² + BE²
... from (i)
=> AD² + CE² = AC² + BD² + BE²
... from (iv)
=> AD² + CE² = AC² + DE²
Substitute AC = 2DE
=> AD² + CE² = (2DE)² + DE²
=> AD² + CE² = 4DE² + DE²
=> AD² + CE² = 5DE²
Hence, proved.