In a right-angled triangle prove that 4 times the sum of the squares on the medians drawn from the acute angles is equal to 5 times the square on the hypotenuse.
Answers
Figure is in the attachment...
In figure ∆ABC, hypotenuse = AC.
Medians = AD & CE.
So we have to prove ; 5AC² = 4(AD² + CE²)
Proof
In ∆ABC ; using Pythagoras theorem :
→ AC² = AB² + BC² ---------- (1)
Now as AD is median drawn on BC, so BD = CD = BC/2
And as CE is median drawn on AB, so AE = BE = AB/2
Now using ∆ABD, using Pythagoras theorem :
→ AD² = AB² + BD²
→ AD² = AB² + (BC/2)²
→ AD² = AB² + (BC²/4)
→ AD² = (4AB² + BC²)/4
→ 4AD² = 4AB² + BC² ------- (2)
Now using ∆BCE ; using Pythagoras theorem :
→ CE² = BE² + BC²
→ CE² = (AB/2)² + BC²
→ CE² = (AB²)/4 + BC²
→ CE² = (AB² + 4BC²)/4
→ 4CE² = 4BC² + AB² --------- (3)
Now adding (2) and (3) :
→ 4AD² + 4CE² = 4AB² + BC² + 4BC² + AB²
→ 4(AD² + CE²) = 5AB² + 5BC²
→ 4(AD² + CE²) = 5(AB² + BC²)
From (1) : AB² + BC² = AC²
→ 5AC² = 4(AD² + CE²) [Proved]
Hence proved ; in a right angled triangle 4 times the sum of the squares on the medians drawn from the acute angles is equal to 5 times the square on the hypotenuse.
Step-by-step explanation:
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