Differential equations

This program gives some information about the differential equation given by the user. The blue lines represent the tanent of one of the possible solutions in the point. The red lines are different numerical approximations to the solution and the green line is a function the user can put in(usually a particular solution to the equation).

My math professor told the students to make a program like this as an optional project for the year. Finishing it will assure me at least one out of tem points in the final exam.

Edit: I upgraded my program because my professor told me it needed more things. It can now accept sin, cos, ln and abs functions. It also has a new approximation method and it has an english translation (My professor didn't need this, but I think I'm going to need it if I want to put it here). I think I changed a few other less important things.