bonjour,
on cherche A grise = A cercle
A gris = A rectangle- A cercle
A rectangle = AB*AD
AB = 8
AD = diametre du cercle = 2x
A rectangle = 16x
A cercle = pix²
A gris = 16x-pix²
A cercle = pix²
16x-pix² = pix²
16x = pix²+pix²
16x = 2pix²
16 = 2pix
x = 16/2pi = 8/pi