I am having trouble with this measure of a cone. I am trying to calculate the slant with the Pythagorean theorem. The measurements are a diameter of 8 and a height of 9. I keep multiplying (8 x 8) + (9 x 9) and I get 145 which I square root it to get 12.04 which equals answer d. But I know that the answer is 9.8 which I just cannot get? Please help I am not trying to cheat but to learn