Getting started Go to geogebra.org, click on ‘webstart’ to launch Geogebra The window is split into three areas: The toolbar is where you can find tools to select objects, draw points, lines, perpendiculars, polygons, circles and other items. Notice each tool ‘drops down’ to reveal more tools. The ‘Algebra’ window shows detailed information about all objects The drawing area is where you construct geometric figures The input field at the bottom can be used to input functions for graphing

Stick man Play around a bit: draw a few points, lines, parallel lines, angles, triangles, etc. Advanced stick man: arms and legs are parallel and move in tandem Turn axes and labeling off, then draw a stick figure similar to the following

Geometry basics Lines and angles Vertical angles and linear pairs Draw two intersecting lines. Use the intersection tool to find the intersection. Find the measure of all 4 angles. Perpendicular lines Parallel lines Be sure the intersection is labeled ? Draw ray AB, then ray AC. Find the measure of the angle by clicking point B, then A, then C. Is that the angle you wanted? If not, undo, and click C, then A, then B. ?

Parallel lines cut by a transversal Draw a line through A and B. Then draw a new point C. Construct a new line through C parallel to the first line. Finally draw another line that intersects these two lines (should be labeled D and E). Find the measure of each of the 8 angles shown. What do you notice? Move around some of the points, what do you notice? ?

Angle, Side Length relationships Triangle Angle Sum What do you get when you add the three angle measures? Construct a triangle. Display all side lengths. Find the measure of each angle. ? ? List the angles in order from smallest to largest. List the side lengths in order from smallest to largest. What do you notice? Change the shape of your triangle. Do you still get the same value?

Proof: Sum of the angles of a triangle is 180° Use the line tool to draw line AB Use the point tool to draw a point C (not on the line) Use the parallel line tool to draw a line through point C parallel to line AB Use the line tool to draw lines AC and BC Use the point tool to draw a new point D such that line CD is parallel to line AB Use the angle tool to define angles CBA, BAC, ACB, and BCD

Proof: Sum of the angles of a triangle is 180°

Parameter changes for a quadratic function Use the slider tool to create three sliders Click the slider tool, then click anywhere in the drawing window, then click enter (this creates a slider named a) Repeat for sliders b and c Next type y=a*x^2+b*x+c (then enter) in the input field Change the values of a, b and c by adjusting the sliders

Parameter changes for a quadratic function