The outer angles B and D of trapezoid ABCD are 105 degrees and 130 degrees, respectively. Find the angle BCD.

The angles CDA and CDM are adjacent angles, the sum of which is 180, then the angle CDA = 180 – 130 = 50.

The sum of the angles of the trapezoid at the lateral side is 180, then the angle ВСD = 180 – 50 = 130.

Answer: The BCD angle is 130.




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