CG=DE+DF证明:连接AD∵DE⊥AB,DF⊥AC∴S△ABD=AB×DE/2, S△ACD=AC×DF/2∵CG⊥AB∴S△ABC=AB×CG/2∵S△ABC=S△ABD+ S△ACD∴AB×CG/2=AB×DE/2+ AC×DF/2∵AB=AC∴CG=DE+DF 施主,我看你骨骼清奇,器宇轩昂,且有慧根,乃是万中无一的武林奇才.潜心修习,将来必成大器,鄙人有个小小的考验请点击在下答案旁的 "选为满意答案"