math

   A 30 foot ladder leaning against a vertical wall makes an angle of 81degree with the ground.     

   How far from the base of the wall is the foot of the ladder?     

   cosine = adjacent over hypotenuse     

          cos ( 81^o )  =  x / 30 ft     

     0.156434465  =  x / 30 ft     

                         x  =  (0.156434465) • 30 ft     

                         x  =  4.693 ft     

   _.