Прямая, параллельная основаниям трапеции ABCD{"color":"#202335","fontFamily":"stix","language":"ru"}, пересекает её боковые стороны АВ{"color":"#202335","fontFamily":"stix","language":"ru"} и CD{"color":"#202335","fontFamily":"stix","language":"ru"} в точках Е{"color":"#202335","fontFamily":"stix","language":"ru"} и F{"color":"#202335","fontFamily":"stix","language":"ru"} соответственно. Найдите длину отрезка EF{"color":"#202335","fontFamily":"stix","language":"ru"}, если AD=35{"color":"#202335","fontFamily":"stix","language":"ru"}, BC=21{"color":"#202335","fontFamily":"stix","language":"ru"}, CF:DF=5:2{"color":"#202335","fontFamily":"stix","language":"ru"}.
