Online Geometry Problem 636: Semicircle, Diameter,
Perpendicular, Inscribed Circle, Common Tangent. Level: High School, Honors Geometry, College,
Mathematics Education

The figure shows the semicircles of diameters AB (center O), and CB (center D). Line CE
is perpendicular to AB and the inscribed circle in ECB
is tangent to semicircle D at G. Prove
that the common tangent GM passes through A.