This is a right triangle. To find the third side of a right triangle. Use the Pythagorean Theorem. a^2+b^2=c^2 a and b are the legs, c is the hypotenuse. a^2+7^2=16^2 a^2+49=256 Subtract 49 from both sides: a^2=207 Square foot: a=14.38749457 in. Round to nearest tenth: 14.4 in