Bonsoir,
1)
2piR
2*3,14 * 5 = 10pi =>31,4 cm
2)
2pi *1,5 => 3pi =>9,4cm
3)
( 2*pi* 4)/2 = 4 pi => 12,56 cm
4)
(2pir)/2 = pir = 4pi = 12,56 cm
5)
(2pir) *3/4 = 6pir /4 = 3pir/2 => 14,13 cm