In a right-angled triangle, one of the acute angles is 72 degrees. Find the degree measure of the other acute angle.

1) The sum of the angles of any triangle is 180 °.
2) We know that this triangle has one angle of a straight line, that is, it is equal to 90 °, and the second angle is 72 °.
3) Find the third angle by subtracting the first two angles from 180o: 180o – 90o – 72o = 18o. We get that the desired angle is 18 °.
ANSWER: 18o.