The screen on this page is designed to help students understand transformations of the Sine, Cosine and Tangent functions, by experimenting with the 4 parameters (A, B, C and D).
The general sine function has the form: Asin(Bx + C) + D (similarly with cos or tan ). The x-axis is in degrees. You can select sine, cosine or tangent by clicking the buttons on the bottom left of the screen.
Varying the parameters A, B, C and D has a variety of different effects. It's a good idea to set some of them to zero to see the effect of the others. Try for yourself.
If you tick the "Median Line" box then a line will be drawn in the "middle" of the function to help you understand its equation. Ticking the "Original Line" box means that the original function remains visible while you transform it.

A challenge! - To test your understanding, hitting the "Random" button will generate a random curve. By varying the parameters, try to cover the random line with the other one, and hence find the equation of the random curve. There is usually more than one correct answer.
If you want an easier start, then clicking on "1" at the top of the page will set the program so that only one of A, B, C, D changes on the random curve - the others stay the same. It get more complicated as you click "2", "3" and "4"! Have a go. If the "Easier" box is ticked, then the value of B in the random curve is never negative, which makes things a little easier. Clear the tick if you want to allow negative values of B in the random curve - a trickier challenge.
Have some fun! Studying this function should also help understand functions and their transformations in general.