In triangle ABC, angle C = 60, angle B = 90, height BD is 4 cm, find AB.

Triangle ABC, by condition, is rectangular, then the angle BAC = (180 – BCA – ABC) = (180 – 60 – 90) = 30.

Since BD is the height of triangle ABC, triangle ABD is rectangular, in which leg BD is located opposite angle 30, and then the length of the hypotenuse AB is equal to two lengths of leg BD.

AB = 2 * BD = 2 * 4 = 8 cm.

Answer: The length of the AB side is 8 cm.

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