To find the height, envision it as a third side to a right triangle. We have the first side, with a length of 7cm, and the hypotenuse, with a length of 15cm. When we have two sides of a right triangle with given lengths, we can employ the Pythagorean Theorem.
The Pythagorean Theorem states that the square of the hypotenuse, c, is equal to the sum of the squares of the other two sides, or:
Well, we have a and c, so we can solve for b.
b ≈ 13.27