DSZ积分插件，有需要的朋友自己上传下载-The DSZ integral plug-in, a friend in need to upload their own download

MATALB符号运算自编自用的小程序，要结合txt文档修改下，推导公式很方便-MATALB symbols for the use of small programs, to be combined with the txt document, the derivation formula is very convenient