# The 80-80-20 Triangle Problem, A Derivative

ABC is an isosceles triangle with vertex angle

(This problem has been invented by Sergey Yurin, at the time a ninth grade student, and reported in [Knop].

### Solutions

- Solution #1
- Solution #2
- Solution #3
- Solution #4
- Solution #5
- Solution #6
- Solution #7
- Solution #8
- Solution #9
- Solution #10
- Solution #11

### Reference

- C. Knop,
__A Story with Geometry, or Nine Solutions to One Problem__,*Kvant*, 1993, no 6

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