Question 63917
 use trigonometry  .  
  
  tan 30 = 10/a
 or 1/{(3)^1/2} = 10/a

 or  a = 10 * (3)^(1/2)
       = 10 * 1.73
       = 17.3

    c = sqrt( 100 +  299.29)
      =19.98