<p>求题19图所示系统的闭环传递函数<img max-width="300" src="https://learnfile.20230611.cn/learnAppQuestion/bd/f8/bdf8c690a60ac6ec8ed9579ad520d6b0.jpg" style="width: 100%;height: auto;"><img max-width="300" src="https://learnfile.20230611.cn/learnAppQuestion/e5/5e/e