[1]
kใๅฎๆฐใจใ, ๅบงๆจ็ฉบ้ใซ4็น 0 (0, 0, 0), A (1, 0, 1), B(0, k, 0), C(1, 1, 1)ใ
ๅใ.ใพใ,็นCใไธญๅฟใจใใๅๅพ 1/12 ใฎ็้ขใSใจใใใ
(1) ็นCใใ็ด็ทABใธไธใใใๅ็ทใจ็ด็ทABใฎไบค็นใHใจใใ. ็นHใฎๅบงๆจใ
kใ็จใใฆ่กจใ.
(2) ็ด็ทAB ใจ็้ขSใ็ฐใชใ2็นใงไบคใใใใใชkใฎๅคใฎ็ฏๅฒใๆฑใใ.
(3) ็ด็ทAB ใจ็้ขSใ็ฐใชใ2็นใงไบคใใใจใ, ใใฎ2ใคใฎไบค็นใP,Qใจใใ.
1
โณCPQใฎ้ข็ฉใ
ใจใชใใใใชkใฎๅคใๅ
จใฆๆฑใใ.
10