Xét tam giác ABC vg tại A => AB^2+AC^2=BC^2

                                                  =>      6^2+8^2=BC^2

                                                  =>    36+64= BC^2

                                                  =>    BC= 10

Mà 2AM =<!--[if gte vml 1]> <xml> </xml><![endif]-->BC=<!--[if gte vml 1]> <xml> </xml><![endif]-->10cm
=>AM=5 cm