<p>设y＝lncos<img src="https://learnfile.20230611.cn/learnAppQuestion/7f/55/7f554737b09053abaf1878a2c1a9378e.jpg" style="width: 100%;height: auto;">，求<img src="https://learnfile.20230611.cn/learnAppQuestion/34/9b/349bf17e8f1d23785b7f83757365fffa.jpg" s