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Online Geometry Problem 4. Triangle, Quadrilateral, Angles, 120 Degrees. Level: High School, Honors Geometry, College, Mathematics Education

In the figure below, AD = CD = BC, and angle C = 2(angle A). Prove that x = 120° - angle A. See also Problem 42.
Try to use elementary geometry (Euclid's Elements.)

 

Geometry Problem 4. Triangle, Quadrilateral, Angle. Elearning
 

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