过M作MP//CD交AD于P,并将其延长到Q点,使PQ＝PM,连接AQ则MP是梯形的中位线,可知△APQ≌△DPM所以 S△AQM＝S△APQ+S△APM＝S△DPM+S△APM＝S△ADM＝AD*MN/2设梯形的高为h则：S△ABM+S△CDM=AB*(h/2)/2+CD*(h/2)/2=(AB+...