tə dˈuː ðˈɪs,  ɪz dᵻfˈaɪnd ˌɔn ɐn ˈɪntɚvəl ðæt ɪz lˈɑːɹdʒɚ ðɐn ænd ɪŋklˈuːdz ., ðˈɛn baɪ ðə mˌʌltɪvˈɛɹɪˌeɪt tʃˈeɪn ɹˈuːl, ðə kəmpˈɑːzɪt fˈʌŋkʃən ɪz dˈɪfɚɹˌɛnʃɪəbəl ˈɔn :
To do this,  is defined on an interval that is larger than and includes .), then by the multivariate chain rule, the composite function  is differentiable on :