设<img src="https://static.zxtiku.com/wangke/imgs/topic/2292da2bbce88d91704cb91228312c23.jpg"/>为曲线<img src="https://static.zxtiku.com/wangke/imgs/topic/149825f0168da3a4fcc828c1b4d74dab.jpg"/>，方向为逆时针方向，则<img src="https://static.zxtiku.com/wangke/imgs/topic/a1ae31d71f266674627f9de24b50c056.jpg"/>=<img src="https://static.zxtiku.com/wangke/imgs/topic/c6baea9dd6a71182bba463840f0f61fd.jpg"/>。（）