一个简单计算器。能实现加减乘除 和正余弦，正余切等运算-GOOD！

基于C#2010的多功能计算器，加减乘除，百分号，正余弦等功能的科学计算器，带日历等-Based on C# 2010 multi-function calculator, addition, subtraction, percent sign, sine and cosine functions of the scientific calculator with calendar