没有图,试一下,A为钝角的话
BE,CF为高
∠EBA+∠BAE=90
∠NCA+∠FAC=90
∠BAE=∠CAF
∠EBA=∠NCA
BM=AC,AB=CN
△MBA≌△ACN
AM=AN
(2)
∠EAN=∠N+∠NCA
∠EMA=∠EBA+∠MAB
∠EMA+∠EAM=90
90-∠EAM=∠EBA+∠MAB
∠NCA+∠N+EAM=90
∠EAN+∠EAM=90
∠MAN=90