Geometry Problem

Level: Mathematics Education, High School, Honors Geometry, College.

Click the figure below to see the complete problem 631.

## Wednesday, July 6, 2011

### Problem 631: Triangle, Exterior Angle Bisectors, Collinear Points

Labels:
angle bisector,
collinear,
point,
triangle

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Since BB’, AA’ and C’C are external angle bisectors so

ReplyDeleteWe have B’C/B’A= a/c

C’A/C’B=b/a

And A’B/A’C=c/b

And (B’A).(C’A/C’B).(A’B/A’C)=a/c.b/a.c/b= 1

So C’, A’ and B’ are collinear per Menelaus theorem

Peter Tran

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