计算器

支持三角函数/反三角函数，乘方，开方，阶乘，求和等基本运算
支持复数运算（直接输入),并支持角度表示和实部虚部表示之间的切换。
支持12个自定义函数 Support basic operations such as trigonometric / inverse trigonometric functions, involution, evolution, factorial, summation
Support complex operations (direct input), and the support angle and switching between the real and imaginary.
Support 12 custom functions