Биссектрисы углов А{"color":"#202335","fontFamily":"stix","language":"ru"} и В{"color":"#202335","fontFamily":"stix","language":"ru"} при боковой стороне АВ{"color":"#202335","fontFamily":"stix","language":"ru"} трапеции ABCD{"color":"#202335","fontFamily":"stix","language":"ru"} пересекаются в точке F{"color":"#202335","fontFamily":"stix","language":"ru"}. Найдите АВ{"color":"#202335","fontFamily":"stix","language":"ru"}, если AF=21{"color":"#202335","fontFamily":"stix","language":"ru"}, BF=20{"color":"#202335","fontFamily":"stix","language":"ru"}.
