当<img src="https://static.zxtiku.com/wangke/imgs/topic/ac6d8ce0e61f3b5e15ef4f319c7f94b3.png"/>时，<img src="https://static.zxtiku.com/wangke/imgs/topic/fcd7cf88f60eb2ade88e8284bc60e6f3.png"/>与<img src="https://static.zxtiku.com/wangke/imgs/topic/b48e84b761fef315486ac5775739744d.png"/>等价