这是本人做的一个计算器，可以计算+-*/cos sin tan asin atan，还可以识别括号，大家快来看看哈-This the one I do calculators, calculation -* / cos sin tan asin atan can also identify brackets, we hurry to see Kazakhstan

atan returns the arctangent of its double-precision argument, Device Driver for linux v2.13.6.

The algorithm is based on atan(x)=atan(y)+atan((x-y) (1+xy)). We use poly1(x) to approximate atan(x) for x in [0,1 8] with error (relative).