Tentukanlah besar sudut abc, acb, acg, fcg

<Abc= 180°-120°= 60°

<Acb= 180°-60°-55°= 65°

<Acg= 180°-65°= 115°

<Fcg= 180°-115°= 65°

ABC = 180 - ABD
ABC = 180 - 120
ABC = 60

ACB = 180 - (60 + 55)
ACB = 180 - (115)
ACB = 65

ACG = 180 - ACB
ACG = 180 - 65
ACG = 115

FCG = ACB
FCG = 65