Bonjour,
a)
BC = CD = DE = 6,8/ 2 = 3,4
(AB*AF) +( CD*DE )
(5,1* 6,8) + (3,4 * 3,4)
= 34,68 + 11,56
=> 46,24 cm²
b)
TO = =3cm
RO = 4+1= 5
RG = 4
GI = 2
(TO*RO)/2 + ( RG * GI)/2
= (3*5)/2 + ( 4* 2)/2
= 15/2 + 8/2
= 7,5 + 4
=> 11,5cm²
c)
3,14 * 3,4²
= 3,14 * 11,56
= > 36, 30cm²
