Finding Equations of Lines in Photos

This is a set of applets I made using Geogebra. In each applet you fit linear equations, in slope-intercept form and point-slope form, to linear elements of photographs. The applets are all the same except that each uses a different photograph. I also developed a worksheet to go along with the applets, and it is included at the bottom of each applet.

Graph

Graph, by Ivan Johansen, is a free, open-source program for Windows that allows you to quickly and easily graph functions while giving you a lot of control over the appearance of the output. The images can be easily pasted into a word processing document and I found that the quality of the printed output when I pasted into Word was quite good. An excellent feature is an option which will label tick marks with any specified multiple of pi.

In fact, the program allows you to do a lot more than make just pretty pictures. For example, you can graph (and obtain the equation of) the line tangent to a function at a specified point or fit a line to a set of points.