• 加法(x+y)
• 减法(x-y)
• 乘法(x*y或(X)(Y))
• 分部(x/y)
• 指数(根的x^y或x^(1/y))
• The following functions: sin, cos, tan, asin, acos, atan, abs
• Single variable evaluation (include "x" in the expression string)