# Geometry Problem 1308

### Quadrilateral, Diagonal, Triangle, Incircle, Tangent Line, Sides, Measurement

The figure below shows a quadrilateral ABCD with sides a, b, c, and d. The
incircles of triangles ABC and ADC are tangent to AC at E, and F,
respectively. Prove that EF = (b + d - a - c)/2.

Geometry Problems

1301-1310

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