# Inner angles

The magnitude of the internal angle at the main vertex C of the isosceles triangle ABC is 72°. The line p, parallel to the base of this triangle, divides the triangle into a trapezoid and a smaller triangle. How big are the inner angles of the trapezoid?

Correct result:

A =  54 °
B =  54 °
C =  126 °
D =  126 °

#### Solution:

$B=\beta =54=5{4}^{\circ }$

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