a)
lg= 4 * lung semicercului= 4 * 2*pi r /2=4 * pi * r
r=10/2=5
lung gard= 4 * pi * 5=20 pi
b) aria = aria patratului + 4* aria semidiscului=
= L patrat + 4*pi r patrat/2
=10 patrat+4*pi 5 patrat/2
=100+50 pi=
=50(pi+2) mp
c)aria =5000(pi+2) dmp
aria necesara pt 1028 tr este 1028*25=25700 dmp
25700 < 5000(pi+2) echivalent cu
25700 < 10000+5000pi ech
15700 < 5000pi ech
314 < 100pi ech
3,14 < pi adevarat