2007 iTest Problems/Problem TB4

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Problem

Circle $O$ is the circumcircle of non-isosceles triangle $ABC$. The tangent lines to circle $O$ at points $B$ and $C$ intersect at $L_a$, and the tangents at $A$ and $C$ intersect at $L_b$. The external angle bisectors of triangle $ABC$ at $B$ and $C$ meet at $I_a$ and the external bisectors at $A$ and $C$ intersect at $I_b$. Prove that lines $L_aI_a$, $L_bI_b$, and $AB$ are concurrent.

Solution

See also

2007 iTest (Problems)
Preceded by:
Problem TB3
Followed by:
Problem Last Question
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 TB1 TB2 TB3 TB4
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