An interactive applet and associated web page that provide step-by-step instructions on how to draw an ellipse using two pins and some string. Not strictly a Euclidean construction, but instructive about ellipses. The animation can be run either continuously like a video, or single stepped to allow classroom discussion and thought between steps. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that provide step-by-step instructions on how to construct an equilateral triangle with a given side length using only a compass and straightedge. The animation can be run either continuously like a video, or single stepped to allow classroom discussion and thought between steps. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that provide step-by-step animated instructions on how to construct a line parallel to a given line through a given point off the line. The animation can be run either continuously like a video, or single stepped to allow classroom discussion and thought between steps. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that provide step-by-step animated instructions on how to construct a perpendicular to a given line at a given point on the line. The animation can be run either continuously like a video, or single stepped to allow classroom discussion and thought between steps. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that provide step-by-step instructions on how to construct a perpendicular at the endpoint of a ray using only a compass and straightedge. The animation can be run either continuously like a video, or single stepped to allow classroom discussion and thought between steps. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that provide step-by-step animated instructions on how to construct a perpendicular to a given line through a given point off the line. The animation can be run either continuously like a video, or single stepped to allow classroom discussion and thought between steps. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that demonstrate how to construct a tangent to a circle at a given point on the circle, using compass and straightedge. It starts with the given circle and point, and in an animation that can run without stopping or single stepped, shows how to construct the tangent line through that point. The text on the page contains written step-by-step instructions that can be printed. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that provide step-by-step animated instructions on how to construct the circumcenter of a triangle. The animation can be run either continuously like a video, or single stepped to allow classroom discussion and thought between steps. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that demonstrate how to construct the two possible tangents to a circle from an external given point, using compass and straightedge. It starts with the given circle and external point, and in an animation that can run without stopping or single stepped, shows how to construct the two tangent lines. The text on the page contains written step-by-step instructions that can be printed. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that demonstrate how to construct the incenter and incircle of triangle using compass and straightedge. It starts with a given triangle, and using animation that can be run continuously or single step, shows how to first construct the incenter, then using that point, construct the incircle of the given triangle. The text on the page contains written step-by-step instructions that can be printed. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that provide step-by-step animated instructions on how to construct the incenter of a triangle. The animation can be run either continuously like a video, or single stepped to allow classroom discussion and thought between steps. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that provide step-by-step instructions on how to find the centroid of a triangle using only a compass and straightedge. The method used involves constructing two of the triangle's medians. The centroid is where they intersect. The animation can be run either continuously like a video, or single stepped to allow classroom discussion and thought between steps. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that provide step-by-step instructions on how to find a median of a triangle using only a compass and straightedge. The method used involves bisecting one side, then drawing a line from this midpoint to the opposite vertex. The animation can be run either continuously like a video, or single stepped to allow classroom discussion and thought between steps. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that provide step-by-step instructions on how to construct the orthocenter of a triangle using only a compass and straightedge. The method used involves constructing two altitudes of the triangle, which intersect at the orthocenter. The animation can be run either continuously like a video, or single stepped to allow classroom discussion and thought between steps. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that demonstrate the concept of a convex polygon - one where all interior angle are less than 180 degrees. The applet shows an irregular convex polygon initially. The user can drag any vertex, change the number of sides in the range 3..99, and make it regular or irregular. When the polygon is convex, the polygon is so flagged. It is shown that regular polygons are always convex. The goal is to show through experimentation what the concept of convexity really means. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that describe the concept of the coordinate plane (Cartesian Plane). The applet shows the plane, its axes, origin and related controls. The user can drag a point around and see the coordinates change, and click anywhere to create new points. The origin can be dragged to emphasize or eliminate certain quadrants. The grid, axis pointers and coordinates can be turned on and off. The coordinate display can be turned off to permit class exercises and then turned back on the verify the answers. The applet can be printed as it appears on the screen to make handouts. The web page has a narrative description of the concept. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that describe the concept of a point in coordinate geometry. The applet show one point initially, but clicking anywhere adds more. As the points are dragged, the coordinates are seen to change. The grid, axis pointers and coordinates can be turned on and off. The coordinate display can be turned off to permit class exercises and then turned back on the verify the answers. The applet can be printed as it appears on the screen to make handouts. The web page has a narrative description of the concept, including the definitions of abscissa, ordinate, coordinates, ordered pair. The applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that demonstrate the concept of coplanar objects - those that lie in the same plane. The applet presents two planes. In one plane there are two rectangles that can be dragged around and which lie in the same plane always. The other is a rectangle that can be dragged but always lies in a plane orthogonal to the first. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that provide step-by-step instructions on how to copy a line segment using only a compass and straightedge. The animation can be run either continuously like a video, or single stepped to allow classroom discussion and thought between steps. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that provide step-by-step instructions on how to divide a line segment into any number of equal parts, using only a compass and straightedge. The applet starts with a given line segment and ends with that segment divided into n parts. In the applet n=5, but the construction works for any n. The animation can be run either continuously like a video, or single stepped to allow classroom discussion and thought between steps. The text on the page has printable step-by-step instructions. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.