In trapezoid ABCD, it is known that AB is parallel to AD, AB is perpendicular to AD

In trapezoid ABCD, it is known that AB is parallel to AD, AB is perpendicular to AD, BC is equal to CD, angle ABD = 80 degrees. Find the corners of the trapezoid.

Since, by condition, ВС = СD, then the triangle ВСD is isosceles, and therefore the angle СD = СDВ.

Angle CBD = ABC – ABD = 90 – 80 = 10.

The angle CBD = CDB = 10, then the angle BCD = 180 – 10 – 10 = 160.

In a trapezoid, the sum of the angles adjacent to the lateral side is 180.

Angle ВСD + АDC = 180, then АDC = 180 – 160 = 20.

Answer: The angles of the trapezoid are 90, 90, 160, 20.



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