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  Problem 13. Triangle, Cevian, Angles, Congruence. Level: High School, SAT Prep, College geometry

 

 

 

The figure shows a triangle ABC, angle A = 4x, angle C = 3x, angle CBD = 5x, and AB = CD. Find x. Post a comment or solution.


 

Triangle, Angles, Congruence, Isosceles, Equilateral
 

 

 

"A great discovery solves a great problem, but there is a grain of discovery in the solution of any problem. Your problem may be modest, but if it challenges your curiosity and brings into play your inventive faculties, and if you solve it by your own means, you may experience the tension and enjoy the triumph of discovery. Such expert experiences at a susceptible age may create a taste for mental work and leave their imprint on mind and character for a lifetime." George Polya, 1944

 

HINTS:


Triangle

Proposition: The sum of the measures of the three angles of a triangle is 180.

 

Proposition. The measure of an exterior angle of a triangle equals the sum of the measures of the two non-adjacent interior angles.


 


Isosceles triangle

Proposition: If two sides of a triangle are congruent, the angles opposite these sides are congruent. Also converse.

 


Triangle Congruence A.S.A. If two angles and the included side of one triangle are congruent to the corresponding parts of another, then the triangles are congruent.

 


An equilateral triangle is equiangular: 60-60-60. Also converse.
 

 


 

 

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