Doua unghiuri sunt suplementare daca au suma egala cu 180 de grade.
86 grade 30 secunde + a = 180 grade
86 grade 30 secunde + a = 179 grade 59 minute 60 secunde
a = 179 grade 59 minute 60 secunde - 86 grade 30 secunde
a = 93 grade 59 minute 30 secunde
