( Formula 26 are normal vectors at the intersection points and their scalar product is Formula 27 ) ( formula _ 26 are normal vectors at the intersection points . Their scalar product is formula _ 27 . )
(Frektor 26 adalah vektor biasa di persimpangan dan produk skalar mereka adalah Formula 27) (formula _26 adalah vektor biasa di titik persimpangan. Produk skalar mereka adalah formula _ 27.)