Introduction to Geometer's Sketchpad

Here are several tasks to perform in Geometer's Sketchpad. You should use the program enough to be able to do these tasks with ease. When you open the program, you will see six icons on the left side of the screen. They are, from top to bottom, the arrow tool, the point tool, the compass (or circle) tool, the straightedge tool, the text tool, and the custom tool. The arrow tool is used to select objects. The next three are used to draw points, circles, and lines.

One important thing to know about is how to highlight objects. By clicking on an object it will be highlighted, and then can be used in further constructions. The order in which you highlight objects can affect the resulting construction.

• Draw a point: Click on the point tool, then click where you want a point.
• Draw a line segment: Click on the line tool. The icon should show two points and a segment connecting them. To draw a line segment click the mouse where you want the segment to begin, and holding the mouse, drag it until you get to where you want the line to end, then release the mouse.
• Draw a ray and line: Click and hold the mouse on the line tool until you see three icons. These, from left to right, are the line segment, ray, and line tools. Click on the appropriate one, then click and hold the mouse somewhere on the screen, then drag to get the ray or line.
• Draw a circle: Click on the circle tool, then click and hold the mouse, move to size the circle. Alternatively, if you want a circle centered at a given point, with the circle tool, place the cursor over the point and then draw the circle. If you want the circle centered at a certain point and passing through another point, click on the center and then click on the second point. Finally, click on construct, then circle by center and point. See what happens if you highlight the points in reverse order and construct the circle by center and point. Circles are determined by two points, one being the center and the other being a point on the circle.
• Resize the circle: Click on the arrow tool, then on the point on the circle. Drag this point to resize the circle. Alternatively, click and drag the center.
• Move the circle: Click on the arrow tool, then on the circle away from the point on the circle. Drag to move the circle.
• Draw a triangle: using the line segment tool, draw a line segment. Then draw a second segment starting where the first segment ended. Finally, draw a third segment starting where the second segment ended and ending where the first segment started.
• Resize the triangle: Click the mouse on the arrow tool. Then click on one of the vertices of the triangle (i.e., one of the endpoints), then drag the mouse to resize. Alternatively, click and drag one of the sides.
• Move the triangle: Click the arrow tool. Then click on two of the sides (or the three vertices). Then drag one of the sides.
• Select more than one object: Click on the arrow tool. Click on the objects you wish to select. You should see which objects are selected.
• Draw the interior of a triangle: Click on the arrow tool. Then click on all three vertices of the triangle. You should see large dots over each of them. Click the mouse on the menu item construct, then on polygon interior.
• Draw a four-sided figure: Once you have drawn it, resize it by moving one of the vertices. Notice that you can make many different shapes.
• Draw the four-sided figure's interior.
• Draw an angle bisector. Geometer's Sketchpad views an angle as three points selected in order. The middle point is the vertex, or corner, of the angle. You can then draw the angle by drawing rays from the vertex through the other two points. Once you have drawn and selected three points, click on construct, and then angle bisector. This line should cut the angle into two equal pieces. If it does not appear to do so, look carefully at the order in which you selected your three points, since there are three different angles that can be made from the three points (the three angles of the triangle formed by the three points).
• Find the intersection of two lines, segments, or circles: Draw two line segments (or rays or lines or circles) that cross. With the point tool, put the mouse over the intersection and click. Move one of the line segments and watch what happens to the intersection point. Alternatively, select both line segments, then click on construct, then on intersection.
• Draw perpendicular and parallel lines: Draw a line. Select the line and a point on the line. Then click construct, then perpendicular line. This constructs a line perpendicular to the given line and passing through the given point.  Next, plot a point off of a given line. Select the line and the point. Click construct, then parallel line. This produces a line through the given point and parallel to the given line.
• Label points or sides: Click on the label tool (the one that looks like a hand), then click on whatever you want to label. If you want to change the label, double click on the label (after selecting either the label tool or the arrow tool).
• Open documents: Open the file Square.gsp. It is in the shares directory for the class. Read the instructions once you open it and play around with them accordingly.

• Print documents: Click on file, then on print preview. Click on fit to page if it shows your sketch printing on two pages . Finally, click print. If you click print directly, your document may print on two pages.