tolong dong kak bantu kerjakan.

a)luas=phi×r×r×1/4
=3,14×40×40×1/4
=1256 cm2

keliling=phi×d
d=40×2=80 cm
=3,14×80
=251,2 cm

b)luas=(s×s)-(1/2×phi×r×r)
=(40×40)-(1/2×3,14×20×20)
=1600-628
=972 cm2

keliling=(4s)-(1/2×phi×d)
=(4×40)-(1/2×3,14×40)
=160-62,8
=97,2 cm