In triangle ABC, angle C is straight, angle A is 30 degrees, BC = 25 cm. Find AB.

Triangle ABC is rectangular, since it has a right angle C, it follows that side AB is hypotenuse (since it lies opposite an angle of 90 degrees), and side BC is a leg (lying opposite an angle of 30 degrees. As you know, the side lying opposite an angle of 30 degrees in a right-angled triangle is equal to half of the hypotenuse. Therefore, the hypotenuse AB = BC * 2 = 25 * 2 = 50 centimeters. Answer: 50 centimeters.

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