说明：   一份软件工程作业，写的是一种公式计算器的需求分析文档，详细的介绍了该软件的需求分析，对正在为软件工程作业发愁的同仁们很有帮助哦！不过请下载后参考，不要只是简单的利用。
(A software engineering work, write a formula calculator needs analysis document, a detailed introduction of the software needs analysis, software engineering operations are worried about how helpful colleagues Oh! However, please download the reference, not just simple to use.)