a)
ABC+BAC+BCA=180°
60+90+BCA=180°
150+BCA=180°
BCA=180°-150°
BCA=30°
b)
BCI=ACI=ACB:2=30:2=15°
CBI+=ANI=ABC:2=60:2=30°
BIC+BCI+CBI=180°
BIC+15+30=180°
BIC+45=180°
BIC=180-45=135°
