Réponses

2013-03-29T11:20:54+01:00

A) 1) ABxAB = 6² = 36 cm²
     2) 1/3 x SA x AB² = 1/3 x 8 x 36 = 96 cm3

 

B) 1) coef. de reduction: k = SE/SA = 2/8 = 1/4
      2) a) EF = k x AB = 6/4 = 3/2 cm
           b) EFxEF = 9/4 cm²
           c) 1/3 x SE x EF² = 1/3 x 2 x 9/4 = 3/2 cm3

 

C) 1) Thales : MN/AB = SM/SA
           MN = AB(SM/SA) = 6x/8 = 3x/4 = 0.75x
      2) 1/3 * SM * MN² = 1/3 * x * (0.75x)² = 3x^3/16 = 0.1875x