trig. how to find the indicated variables?

a  =  √ [ 15^2  - 9^2 ]  =  √ [225  - 81 ] =  √ 144   = 12

b =  √ [ 40^2  + 9^2 ]  =  √1681  = 41

c = 9

d = 15

e = b =  41