In triangle ABC, angle C is 90 degrees, BC = 1, sinA = 0.2. Find AB.

If one of the angles in a triangle is 90º, then this triangle is right-angled. So, to calculate the length of the hypotenuse AB, it is most convenient to apply the theorem of sines, according to which, the sine of an acute angle of a right-angled triangle is the ratio of the opposite leg to the hypotenuse:

sin A = BC / AB;

AB = BC / sin A;

AB = 1 / 0.2 = 5 cm.

Answer: the length of the hypotenuse AB is 5 cm.