what must be the length of a ladder that mr. rizzo can use if he wishes to place the bottom of the ladder five feet from a wall and he wishes to reach a window that is 15 feet above the ground? use the pythagorean theorem to solve pls

Which sum or difference identity would you use to verify that cos (180° - q) = -cos q? a.) sin (a -b) = sin a cos b – cos a sin b b.) cos (a -b) = cos a cos b – sin a sin b c.) cos (a -b) = cos a cosb + sin a sin b d.) sin (a + b) = sin a cos b + cos a sin b