Features:

• addition, substraction, multiplication, division and exponantiation
• single letter variables (with optional descriptions of what they hold)
• automatic recalculation of variables upon change of one (can be turned on and off)
• constants: pi
• trigonometric functions: sin, cos, tan (tg), csc, sec, cot (ctg), asin, acos, atan
• logarythmic functions: log, log2, log3, log5, log7, log10
• grouping expressions in brackets
• commands (type 'help' to show all available)

Calculator icon by Papirus Development Team.