pada gambar disamping,panjang AB=17cm,BC=10 cm,dan AC=21 cm.keliling lingkaran luar ABC adalah

s=1/2(a+b+c)
=1/2(17+10+21)
=1/2(48)
=24
r(jari")= abc/4√s(s-a)(s-b)(s-c)@
=17×10×21 / 4√24(24-17)(24-10)(24-21)
=3570 / 4√24×7×14×3
=3570 / 4√2×2×2×3×7×2×7×3
=3570 /4√2²2²3²7²
=3570/ 4×2×2×3×7
=3570 / 336
=10,625
keliling=π×diameter
=π×(2×10,625)
=21,25πcm(B)