Xeˊt Δ ABD coˊ:
∠BAD=50°,∠ADB=90°⇒∠ABD=180°−∠BAD−∠ADB=180°−50°−90°=40°
Vậy ∠ABD=40°
,
Xeˊt Δ ACE coˊ:
∠EAC=50°,∠CEA=90°⇒∠ACE=180°−∠EAC−∠AEC=180°−50°−90°=40°
Vậy ∠ACE=40°
,
Xeˊt tứ giaˊc AEDI coˊ:
∠AEI=90°,∠ADI=90°,∠EAD=50°
⇒∠EID=360°−∠AEI−BICADI−∠EAD=360°−90°−90°−50°=130°
Vậy ∠EID=130° maˋ ∠EID=∠BIC( hai goc đoˆˊi đỉnh)⇒∠BIC=130°
