What is an interactive geometry calculator?
An interactive geometry board connects shapes to points. Move a point and every construction using that point updates. Use it to explore coordinate geometry, or use the Triangle Calculator when you have side lengths or angles instead of coordinates.
How to draw shapes and measure angles
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Enter one point per line, such as A 0 0. Choose Build Board, then use the point and construction controls. You can also type commands directly, one per line. For example, circle A B puts the center at A and the edge at B. angle A B C measures at B. Use Add points and tap inside the grid to place another point. Try geometry sets (paid link) when repeating the same exercise on paper.
How lengths, areas and angles are calculated
Distances come from the horizontal and vertical differences. A triangle’s area is half the absolute determinant of two sides. The smaller angle uses the determinant and dot product of the arms and is shown in degrees. For standalone calculations from a known radius or area, use the Circle Calculator.
How to read the coordinate diagram
Both axes use the same scale. Change the board range if points are outside the visible grid. Dragging updates the coordinates to hundredths. For a more precise placement, type coordinates directly. Use protractors (paid link) to compare a sketched angle with the value on the board.
Worked example: draw a 3–4–5 triangle
Enter A 0 0, B 4 0 and C 0 3 on separate lines. Add triangle A B C and angle B A C. The area is 6 square coordinate units, the perimeter is 12 coordinate units and the angle at A is 90°. Drag C vertically to see what changes. Record the coordinate pairs in graph-paper notebooks (paid link).
Supported constructions and limits
Use up to 16 labeled points and 12 constructions. Coordinates can range from −100 to 100 with up to six decimal places. Lines and circles require two different locations, and each arm of an angle needs positive length. This board uses numerical coordinates and measurements. Formal proofs, dependent intersection points and compass-and-straightedge constraints are outside its scope. Use geometry workbooks (paid link) to practice those constructions by hand.
Interactive Geometry Calculator FAQs
Yes. Edit the named point in the Coordinates box and select Build Board again.
The middle point. In angle A B C, B is the vertex and the calculator reports the smaller angle from 0° to 180°.
The board clips drawings at the window boundary. Increase the board range to see more of the construction.
Sources and methodology
These resources explain the concepts and browser behavior behind this independent tool.