Angles Simulation: Protractor, Pairs, Parallel Lines

The Angles Lab covers everything about angles from Class 5 to Class 11 in 25 short interactive labs, rebuilt from GeoGebra's “Learn Angles” collection. It starts with what an angle is — two rays (the arms) from one point (the vertex) — with a magnifying glass you slide over the figure to find all seven parts, and letter tiles to name an angle three ways: ∠ABC, ∠CBA, or ∠B when only one angle has its vertex at B. A dial shows acute, right, obtuse, straight and reflex angles, and a 3D room of everyday objects — a clock, scissors, a laptop, a door and a book, all moving by themselves — asks you to freeze each one and say what kind of angle it makes.

Measuring and drawing are done with a real protractor that you drag onto the vertex and turn onto an arm; the step-by-step solution slides it into place and lights up the right scale, the one that reads 0 on the first arm (the other scale gives 180° minus the angle, the slip behind “an obtuse angle of 37°”). There is an angle-sense game, played in degrees and in radians, which awards points for drawing or estimating without tools, and a hot-and-cold game. Pairs of angles come next: adjacent angles add, complementary and supplementary pairs slide together into a right angle or a straight line, vertical angles are shown equal by spinning one half a turn, and “find x” drills turn each rule into an equation.

With parallel lines, the lab uses GeoGebra's picture of two parallel roads crossed by a third, with cars driving along them: click any of the eight angles and its partner lights up, while a copy slides along the crossing road (corresponding angles), spins half a turn about the midpoint (alternate angles) or moves across to form a straight line (co-interior angles). Then come the converse — which lines must be parallel — the triangle whose corners tear off and line up into 180°, polygons split into n − 2 triangles, the exterior-angle walk that turns exactly 360°, and radians: a string as long as the radius wraps round the circle, π of them fill a semicircle, and a conversion table fills in as you visit angles. Every practice question gives three CHECKs, a hint after the second and the worked solution after the third.