Three synthetic proofs of the Butterfly Theorem - Nguyen Tien Dung We give three synthetic proofs of the butterfly theorem, using Thales' theorem, the notions of isogonal conjugates, and spiral similarity respectively. ✪ ✪ ✪ ✪ ✪ Link tải tài liệu: LINK TẢI TÀI LIỆU Theo LTTK Education