Which of the following is the pythagorean theorem?

a. in an obtuse triangle, the sum of the squares of the leg lengths is less than the square of the hypotenuse length.

b. in a right triangle, the sum of the squares of the leg lengths is less than the square of the hypotenuse length.

c. in an obtuse triangle, the sum of the squares of the leg lengths is equal to the square of the hypotenuse length.

d. in a right triangle, the sum of the squares of the leg lengths is equal to the square of the hypotenuse length.