[FEATURE] Mathematical functions and graph drawing

[tommens]

Describe the new functionality you would like to see

• The calculator should be able to manipulate mathematical functions instead of only numerical values. The mathematical functions should containing a single variable x (corresponding to mathematical functions f(x) with argument x). For example, one could represent the following expressions: sin(x), (x^2)+(2*x)+1, (x-1)^2, exp(x^2) assuming that sin, exp, +, - and ^ are predefined functions known to the calculator.
• The calculator needs to be able to plot/draw such functions on the screen. This drawing functionality could be combined with zooming in and out, panning, and so on…

Illustration
An example illustrating how the intended functionality could potentially look like (based on the interface proposed by https://web2.0calc.com) is shown below: