题目

阅读短文，判断正(T)误(F)Hi, friends. Look at my photo. This is my grandfather. He is very old and very thin. This is my grandmother. She is very old too. They are retired(已退休的). This is my father. He is tall. He is a driver. This is my mother. She is beautiful. She is a teacher. She teaches English. This is me. I’m a pupil and I’m a boy. ( ) 1. Grandfather is very old and very fat. ( ) 2. Grandmother is very old. ( ) 3. Father is very short. ( ) 4. Father is a driver. ( ) 5. Mother is a teacher,and she teaches English.如图，已知圆O：x2+y2=1，O为坐标原点．（1）边长为的正方形ABCD的顶点A、B均在圆O上，C、D在圆O外，当点A在圆O上运动时，C点的轨迹为E．①求轨迹E的方程；②过轨迹E上一定点P（x，y）作相互垂直的两条直线l1，l2，并且使它们分别与圆O、轨迹E相交，设l1被圆O截得的弦长为a，设l2被轨迹E截得的弦长为b，求a+b的最大值．（2）正方形ABCD的一边AB为圆O的一条弦，求线段OC长度的最值．