Réponse :

EX1

1)  a) p = 2πr = 2 π x 13 = 26 π cm  ≈ 81.7 cm

   b) A = πr² = π x 13² = 169 π cm² ≈ 530.93 cm²

2) a) p = πD = 28 π m ≈ 88 m

   b) A = πD²/4 = π x 28²/4  = 196 π m² ≈ 615.8 m

ex2

1)  A = 1/2(12 x 7) = 42 cm²

2) A = 1/2(13 x 8) = 52 cm²

3) A = 1/2( 4 x 6) = 12 cm²

4) A = 15 x 8 = 120 cm²

5) A = 9 x 3 = 27 cm²    

Explications étape par étape :