ðɪ ˌɪntɚsˈɛkʃən ʌv sˌiːˈɛs ænd sˌiːtˈiː ɪz ðə sˈɛt ʌv lˈaɪnz ˌɔn ˈɛf ðæt kˈʌts ðə dɪsdʒˈɔɪnt lˈaɪnz ˌɛlˈɛs ænd ˌɛltˈiː. kənsˈɪdɚ ðə lˈɪnɪɹ spˈæn ʌv ˌɛlˈɛs ænd ˌɛltˈiː : ɪɾ ɪz æn hˌaɪpɚplˈeɪn ˌɪntʊ pˈiː fˈoːɹ ðæt kˈʌts ˈɛf ˌɪntʊ ɐ smˈuːð kjˈuːbɪk sˈɜːfɪs.
The intersection of Cs and Ct is the set of lines on F that cuts the disjoint lines Ls and Lt. Consider the linear span of Ls and Lt : it is an hyperplane into P4 that cuts F into a smooth cubic surface.