Triangles & Quadrilaterals

A random triangle appears — read its three angles and decide whether it is acute, right, or obtuse. A correct answer lights up a green glow box and explains the reason.

Drag the sliders to change the three side lengths and watch live: when it closes, the two shorter sides meet; when it fails, they lie flat and cannot reach the longest side. Three check chips compare every pair-sum with the third side.

A random triangle appears — tap its three corners to tear the angles off and lay them along a straight line. They exactly fill a straight angle. Try new triangles and discover the sum is always 180°.

Drag two sliders to reshape a quadrilateral: top width and top tilt. The canvas highlights live whether each pair of opposite sides is parallel (with tick marks) and classifies the shape as parallelogram, trapezoid, or general quadrilateral. Can you turn a trapezoid into a parallelogram?