DC//AB,AE=AB=DC
△MDC≡△MAE
MA=MD,MA=1/2AD=AB=AE
∠AEM=∠AME
∠DAF=∠AEM+∠AME=2∠AEM
同理∠CBA=2∠AFD
∠DAF+∠CBA=2∠AEM+2∠AFD=180
∠AEM+∠AFD=90
EC垂直FD
DC//AB,AE=AB=DC
△MDC≡△MAE
MA=MD,MA=1/2AD=AB=AE
∠AEM=∠AME
∠DAF=∠AEM+∠AME=2∠AEM
同理∠CBA=2∠AFD
∠DAF+∠CBA=2∠AEM+2∠AFD=180
∠AEM+∠AFD=90
EC垂直FD