题目

Many people know the names Alexander Graham Bell and Thomas Edison. However, most people don’t know the name of the man who invented the television, Philo Farnsworth. Philo Farnsworth was born in 1906 and grew up on a potato farm. As a boy, he loved to learn about science, and he read a lot of science books. When he was only thirteen years old, he drew a picture of a machine that could send pictures as radio sends sounds. He got the idea from the way the potatoes were planted in the field. The potatoes grew in long lines, side by side. This made a shape（形状） in Philo’s mind.已知:E为DF上一点，B为AC上的一点，∠1=∠2，∠C=∠D.试判断DF与AC的位置关系，并说明理由.