[2, 10] fct densite : 1/10-2 = 10/8 P(X<=5) = 5-2/10-2 = 3/8 P(6<=X<=8) = 8-6/10-2 P(X<=5 & X>=3) = P(X<=5 & X>=3)/ P(X>=3) ex : [5,10] P(X>7) = 10-7/10-5 ex : [4,20] P(x>8) (8<X<12): 12-8/20-8 E(x)= b+a / 2 ecart type Ecart = rac de V au 2 b-a / 2 rac de 3