1. In ∆ ABC, AD is a median. If AB = 8, AC = 15
and AD = 8.5, find BC.
Answers
Given :-
- AD is a median.
- AB = 8
- AC = 15
- AD = 8.5.
To Find :-
- BC ?
Solution :-
Since AD is a median . using Apolloniu's Theorem we get,
→ AB² + AC² = 2(AD² + BD²)
Putting all values we get,
→ 8² + 15² = 2(8.5² + BD²)
→ 64 + 225 = 2(72.25 + BD²)
→ 289 = 144.5 + 2BD²
→ 2BD² = 289 - 144.5
→ 2BD² = 144.5
→ BD² = 72.25
→ BD² = (8.5)²
Square - root both sides,
→ BD = 8.5
Therefore,
→ BD = DC = 8.5 (AD is median.)
Hence,
→ BC = 8.5 * 2 = 17 . (Ans.)
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