Material Detail

A free, no-sign-up reference for plane and solid geometry: 23 individually usable resources covering 20 shapes — square, rectangle, triangle, right triangle, circle, arc, sector, chord, trapezoid, parallelogram, rhombus, regular polygon, cube, rectangular prism, triangular prism, cylinder, cone, sphere, hemisphere and pyramid — plus coordinate geometry (distance, midpoint and slope).

Each resource is answer-first: the formula, a labelled diagram, a worked example with real numbers, and an interactive explorer whose sliders drive the diagram, the results and a step-by-step substitution panel simultaneously. Every explorer is operable by keyboard alone, and mathematics is rendered as reflowable HTML rather than images, so it zooms and is readable by screen readers.

On content quality: every formula is computationally verified before publication. A test script checks each shape's compute function against independently known values — the 3-4-5 triangle, the unit circle, a sphere of radius 3 whose volume and surface area both equal 36π — 122 assertions in total. The printed formula, the worked example and the live explorer all render from that same verified function, so they cannot drift apart.

On teaching support: the /educators/ page documents the intended audience, learning objectives and Common Core alignment for all 23 resources, with a CCSSM index mapping 23 standards (8.G.C.9, HSG.GMD.A.3 and HSG.GPE.B.7 among them) to the resources that teach them. Each resource page also carries its own objectives, aligned standards and a suggested classroom activity.

A formula-sheet builder generates printable one-page references, with presets matched to the Regents, STAAR, SOL, Keystone, SAT and ACT reference sheets. Any explorer embeds in a class site or LMS with one line of HTML. Core pages are available in Spanish.

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