Engineering
Mathematics
A Circle
Question

Triangle ABC is right angled at A. The circle with centre A and radius AB cuts BC and AC internally at D and E respectively. If BD = 20 and DC = 16 then the length AC equals

626

621

30

32

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Solution

b2 + r2 = (36)2    ....(1)
Also    CD · CB = CE · CX  (using power of the point C)
16 · 36 = (b – r)(b + r)
∴ b2 – r2 = 16 · 36

                    
from (1) and (2)
2b2 = 36(36 + 16) = 36 · 52
b2 = 36 · 26 ⟹  b = 626

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