Explicație pas cu pas:
ΔABC=Δdreptunghic , AA'=bisect ∡A=>∡A=45°
m(∡B)=70°
BB'=bisect ∡B=>∡A=35°
ΔAIB=∡A+∡I+∡B=180°=45°+∡AIB+35°=180°
=∡AIB=180°-80°=100°
ΔABC=∡A+∡B+∡C=90°+70°+∡C=180°
=∡C=180°-160°=20°
CC'=bisect ∡C=>∡C=10°
ΔAIC=∡A+∡AIC+∡C=45°+∡AIC+10°=180°
=∡AIC=180°-55°=125°
ΔCIB=∡C+∡CIB+∡B=10°+∡CIB+35°=180°
=∡CIB=180°-45°=135°
