An interactive applet and associated web page that provide step-by-step instructions on how to copy a given triangle 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 demonstrate the corresponding angles that are formed where a transversal crosses two lines. The applets cycles through the four possible pairs of angles when in animation mode. By dragging the three lines, it can be seen that the angle pairs are congruent only when the lines are parallel. When not in animated mode, there is a button that cycles through each the four pairs of angles. The text on the page discusses the properties of the pairs of corresponding angles both in the parallel and non-parallel cases. 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 properties of a cube. A 3-D cube is shown in the applet which can be interactively manipulated using the mouse. Research has shown that some younger students have difficulty visualizing the parts of a 3D object that are hidden. To help with this, the student can rotate the cube in any axis simply by dragging it with the mouse. It can also be 'exploded' - where a slider gradually separates the faces to reveal the ones behind. The cube can also be made translucent so you see through it to the other side. Applet can be enlarged to full screen size for use with a classroom projector, and printed to make handouts. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet that allows the user to graphically explore the properties of a cubic equation. Specifically, it is designed to foster an intuitive understanding of the effects of changing the 4 coefficients in the function. The applet shows a large graph of a quadratic (ax^3 + bx^2 +cx + d) and has four slider controls, one each for the coefficients a,b,c and d. As the sliders are moved, the graph is redrawn in real time illustrating the effects of these variations. 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.

A web page and interactive applet illustrating the properties of a decagon (10 sided polygon). The applet shows a decagon where the user can drag any vertex to reshape it. User can see that the interior and exterior angles are constant in a regular decagon, but vary in an irregular version. Controls allow the display or hiding of the diagonals, and triangles within the decagon. The web page lists the properties of a decagon including interior angles, exterior angles, sum of exterior angles, area, number of diagonals and number of internal triangles. Links to pages with generalized properties of all polygons. 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 intersection of two lines. The applet shows two line segments with draggable end points. As the lines are moved, the intersection point id continuously updated. If the two segments do not intersect, a message pops up to that effect. 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 properties and behavior of a square. The applets shows a square with all vertices draggable. As you drag any one, the others move to ensure the figure remains a square. It can be seen that the sides remain parallel and congruent, and the interior angles remain 90 degrees 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.

A web page and interactive applet show how to compute the length of the diagonals of a rectangle. A rectangle is shown that can be resized by dragging its vertices. As you drag, the diagonals are continuously recalculated. Text on the page explains calculation. For those who prefer it, in a formula that is given. 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 reference book project at http://www.mathopenref.com.

A web page and interactive applet show how to compute the length of the diagonals of a square. A square is shown that can be resized by dragging its vertices. As you drag, the diagonals are continuously recalculated. Text on the page explains calculation. For those who prefer it, in a formula that is given. 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 reference book project at http://www.mathopenref.com.

An interactive applet and associated web page that demonstrate the diameter of a circle. The applet shows a circle and a diameter line, the ends of which can be dragged to show that the diameter passes through the center and has a constant length regardless of where on the circle it is drawn. The web page has the circle-related formulae. 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 find the distance between two points with given coordinates. The applet has two points on a Cartesian plane. As the user drags either point it continuously recalculates the distance between them. The distance is shown both on the plane and as a continuously changing formula. The grid, axis pointers and coordinates can be turned on and off. The distance calculation 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 full description of the concept of point distance, a worked example and has links to other pages relating to coordinate geometry. 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 find the perpendicular distance between a point and a line. The applet has a line with sliders that adjust its slope and intercept, and a draggable point. As the line is altered or the point dragged, the distance is recalculated. The page actually shows four ways to do it, with links to detail pages on each one. The grid and coordinates can be turned on and off. The distance calculation 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 full description of the concept of the concepts, a worked example and has links to other pages relating to coordinate geometry. 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 find the perpendicular distance between a point and a line using trigonometry, given the coordinates of the point and the slope/intercept of the line. The applet has a line with sliders that adjust its slope and intercept, and a draggable point. As the line is altered or the point dragged, the distance is recalculated. The grid and coordinates can be turned on and off. The distance calculation 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 full description of the concept of the concepts, a worked example and has links to other pages relating to coordinate geometry. 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 find the perpendicular distance between a point and a line that is either vertical or horizontal, given the coordinates of the point and the equation of the line. The user can set the orientation of the line and position, along with the location of the point. As the line is altered or the point dragged, the distance is recalculated. The grid and coordinates can be turned on and off. The distance calculation 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 full description of the concept of the concepts, a worked example and has links to other pages relating to coordinate geometry. 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.

A web page and interactive applet illustrating the properties of a dodecagon (10 sided polygon). The applet shows a dodecagon where the user can drag any vertex to reshape it. User can see that the interior and exterior angles are constant in a regular dodecagon, but vary in an irregular version. Controls allow the display or hiding of the diagonals, and triangles within the dodecagon. The web page lists the properties of a dodecagon including interior angles, exterior angles, sum of exterior angles, area, number of diagonals and number of internal triangles. Links to pages with generalized properties of all polygons. 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 show the definition and properties of an ellipse. The applet has a draggable point that shows that the sum of the distances to the foci is a constant. The web page also has links to other pages defining the various properties of an ellipse and to some ellipse constructions. 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 optical properties of elliptical mirrors. Rays that pass through one focus of an ellipse always a reflected so they pass through the other focus. The ellipse can be resized by dragging, and light rays change to show that this is always true. The web page also has links to other pages defining the various properties of an ellipse and to some ellipse constructions. 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 equation of a line in point-slope form. The user can move a slider that controls the slope, and can drag the point that defines the line. The graph changes accordingly and equation for the line is continuously recalculated with every slider and / or point move. The grid, axis pointers and coordinates can be turned on and off. The equation 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 full description of the concept of the equation of a line in point - slope form, a worked example and has links to other pages relating to coordinate geometry. 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 equation of a line in coordinate geometry. The equation is in the form y=mx+b. The user can move two sliders that control a and b. The graph changes accordingly and equation for the line is continuously recalculated with every slider move. The grid, axis pointers and coordinates can be turned on and off. The equation 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 full description of the concept of the equation of a line, a worked example and has links to other pages relating to coordinate geometry. 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 equiangular triangles (all interior angles congruent). The applet presents an equiangular triangle where the user can drag any vertex. As the vertex is dragged, the others move automatically to keep the triangle equiangular. The angles and side lengths are updated continuously to show that the all interior angles are always congruent. 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.