The hydrogen atoms on both the front and rear carbon atoms have an angle of 120° between them, resulting from the projection of the base of the tetrahedron onto a flat plane.
ðə hˈaɪdɹədʒən ˈæɾəmz ˌɔn bˈoʊθ ðə fɹˈʌnt ænd ɹˈɪɹ kˈɑːɹbən ˈæɾəmz hæv ɐn ˈæŋɡəl ʌv wˈʌnhˈʌndɹɪd twˈɛnti dᵻɡɹˈiːz bᵻtwˈiːn ðˌɛm, ɹɪzˈʌltɪŋ fɹʌmðə pɹədʒˈɛkʃən ʌvðə bˈeɪs ʌvðə tˌɛtɹɐhˈiːdɹən ˌɑːntʊ ɐ flˈæt plˈeɪn.