If two of the legs of a right triangle are 9 and 12, what is the length of the hypotenuse

In the right angled triangle, a hypotenuse is the longest line of the triangle and is always the one that is opposite the right-angle of the triangle.

If your triangle is a right angled triangle, the simplest way is to use the Pythagora's Theorem to find the length of the hypotenuse. The formula for which is

a² + b² = c² where c is the unknown hypotenuse and a and b are the other two sides.

Using this formula,

9² + 12² = c²

89 + 144 = c²

233 = c²

√233 = √c²

15.25 = c which is you see is also the lengthiest ...