Triangle solver
Set the sides or the angles and watch it draw the triangle for you.
What the Triangle solver does
Give it three sides, or two sides and the angle between them, and it builds the triangle to scale. It refuses to draw one that cannot exist, which is itself the answer to a lot of homework questions.
Set the sides or the angles and it draws the triangle to scale. Then drag a corner: every side, every angle and the area update as you move, so you can see why the rules hold instead of being told that they do.
It is for the geometry homework where a static diagram fails hardest: proving that the angles add to 180, seeing what happens to the area as a triangle gets flatter, finding the shape that satisfies two constraints at once. It refuses to draw a triangle that cannot exist, which is itself the answer to a lot of questions.
More tools
A calculator, a grapher, a triangle solver, an equation balancer and a Python console. All of them run in your browser, all of them are free, and none of them need an account.
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- Python consoleReal Python running in your browser, with charts and a console.
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More about the Triangle solver
When you are clearly aiming for an exact angle, it locks on: hover near 90 or 60 for a couple of seconds and the corner snaps to it and holds. Tap an angle to pin it, and it stays fixed while you drag anything else. It does the same for two equal angles, so an isosceles triangle is easy to make.
Chat about this hands the shape, with its measurements, into the conversation. Ask for the proof, ask for the missing side by the law of cosines, or ask why the pinned angle forced the others to change.
Why ours is better
It snaps only when you mean it.
The first version grabbed every angle near a round number and fought the student. The snapping is now dwell-based: nothing moves until you have held near the target for two seconds, and it lets go when you leave.
Angles can be pinned.
Lock one or two angles and drag the rest. Two pins settle against each other exactly, with the angles still adding to 180, which is how a construction problem is actually explored.
Every number is computed, not recalled.
Sides, angles and area come from the coordinates, in your browser, every time. There is no model that could get it wrong.
How it was built
The snapping and the pinning share one piece of geometry: a function that finds where a corner must sit for a given angle to be exact, either by rotating it about a neighbor or by sliding it onto the arc from which the opposite side subtends that angle. Because both go through it, they can never disagree about where an exact angle is.
It was tuned against real complaints: a right angle that was too hard to reach, then a magnet that was too eager, then two base angles that would not come out equal. Each fix was measured in a test harness before it shipped, and the tool runs entirely on your device.
Keep what you work on
A free account keeps your questions together by class, remembers what you have covered, and gives you a weekly allowance rather than a daily one.