In parallelogram ABCD, the height BH is half the side of CD. Find the degree measure of the angle ABC.

Since the opposite sides of the parallelogram are equal, then AB = СD.

By condition, ВН = СD / 2, then in a right-angled triangle AВН, ВН = AB / 2.

Then SinВAD = ВН / AB = (AB / 2) / AB = 1/2.

Angle ВAD = arcsin (1/2) = 30.

In a parallelogram, the sum of adjacent angles is 180, then the angle ABC = 180 – ВAD = 180 – 30 = 150.

Answer: Angle ABC is 150.



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