(1)解:∵AA1⊥面ABC,∴AA1⊥BC,
又BC⊥AC,且AA1∩AC=A,∴BC⊥面AC1
∴BC是三棱锥B﹣DCC1的高.
Vc1-
①无理数就是开方开不尽的数;
②无理数是无限不循环小数;
③无理数包括正无理数,零,负无理数;
④无理数都可以用数轴上的点来表示.
— Jim, can you help me to wash the dishes?
— Sorry, Dad. I ________ to play football.