which is the formula used for the surface area of a general functional shape. One can recognize the vector in the second line above as the normal vector to the surface.
w ɪ t̠ʃ WORD_BOUNDARY ɪ z WORD_BOUNDARY ð ə WORD_BOUNDARY f ɔ ɹ m j ʊ l ə WORD_BOUNDARY j uː z d WORD_BOUNDARY f ə ɹ ð ə WORD_BOUNDARY s ɜː f ɪ s WORD_BOUNDARY ɛ ɹ iə WORD_BOUNDARY ə v ə WORD_BOUNDARY d̠ʒ ɛ n ə ɹ ɹ ə l WORD_BOUNDARY f ʌ ŋ k ʃ ə n ə l WORD_BOUNDARY ʃ eɪ p WORD_BOUNDARY w ʌ n WORD_BOUNDARY k æ n WORD_BOUNDARY ɹ ɛ k ə ɡ n aɪ z WORD_BOUNDARY ð ə WORD_BOUNDARY v ɛ k t ə ɹ ɹ WORD_BOUNDARY ɪ n ð ə WORD_BOUNDARY s ɛ k ə n d WORD_BOUNDARY l aɪ n WORD_BOUNDARY ə b ʌ v WORD_BOUNDARY æ z WORD_BOUNDARY ð ə WORD_BOUNDARY n ɔ ɹ m ə l WORD_BOUNDARY v ɛ k t ə ɹ WORD_BOUNDARY t ə WORD_BOUNDARY ð ə WORD_BOUNDARY s ɜː f ɪ s WORD_BOUNDARY