Take the square root of the sum of the two sides squared for the side required.
Example.—Required the length of the interior slope of a rampart, whose perpendicular height is 17 feet, and the base of the slope 20 feet.
17 × 17 = 289
20 × 20 = 400
The square root of 689 = 26·24. The length required.
2. When the hypothenuse, and one of the perpendicular sides are given.
From the square of the hypothenuse, subtract the square of the given side, and the square root of the remainder will be the side required.
Example.—The hypothenuse being 5 yards, and the base 4 yards, required the other side.
5 × 5 = 25
4 × 4 = 16
The square root of 9 = 3 yards. The side required.
To find the area of a trapezium, A B C D.