Mathematical expressions and functions 

Mathematical expression is the exact operations description, which operations produce numerical value. They are the analogs of mathematical formulas. Syntactically, the math expression is the combination of the numbers, numerical variables and numerical functions, separated by the signs of the math operations and the parentheses. The simplest examples of math expressions are the number and the numerical variable Following math operations are allowed in the language:
It is necessary to remember, that two operational sign cannot be placed one after another. To control the order of evaluation use the parenthesis <(> и <)>. Also you can use predefined functions and variables in the expressions. 
