LeoCalculator is an application for performing calculation of mathematical expressions that could include not only basic operations but also functions and brackets. Edit box "Expression" has to contain a string of mathematical expression that is supposed to be calculated. It can contain: numbers in with or without decimal point and with or without a power of 10 like 1.2e-2 or 3.E3; pi in this application is equal to 3.141592653; basic mathematical operations +,-,*,/; power of grade operation ^ used like 2^3 = 8; brackets determining order of operation execution; major functions: sin, cos, tan, asin, acos, atan, ln, log10, exp, pow10, abs, sqrt. Arguments of the functions have to be an expression surrounded brackets; variables determined in the edit box "Definitions"; Edit box "Expression" can contain definitions of variables: variables can be any combinations of letters and numbers without spaces and reserved words: e, E, pi, sin, cos, tan, asin, acos, atan, ln, log10, exp, pow10, abs, sqrt (not case sensitive); value expressions as usual are numbers but in most cases it could be mathematical expressions too. Tip: variable expression that contains other variables should be longer than them. To perform calculation press key "Enter" or print letter "=" after expression you want to calculate. The result will appear after mark "=". You can do standard manipulation with "Expression" edit box such as copy/paste operation. Editing "Expression" box just after calculation will force the disappearance of result. The main idea is that the result value has to correspond with the expression.