点I为△ABC的内心,ID⊥BC于点D,CI的延长线交AB于点E.求证:∠BID=∠EIA.

问题描述:

点I为△ABC的内心,ID⊥BC于点D,CI的延长线交AB于点E.求证:∠BID=∠EIA.

∠BID = 90 - ∠B/2
∠EIA = ∠A +∠C = 90 - ∠B/2
∠BID=∠EIA