- Middle school📐Geometry🔺
Triangle area: half of the surrounding rectangle
Base × height ÷ 2: the formula comes from a rectangle cut in half. The visual proof that makes the formula obvious.
- Middle school📐Geometry🔺
A triangle's angles always sum to 180°
Why 180°? Cut the angles out with scissors — they form a straight line. Proof in 3 animated steps.
- Middle school📐Geometry🔭
Thales' theorem: when triangles zoom
Two lines from the same point, cut by parallels. The lengths stay proportional. The key to measuring without measuring.
- Middle school📐Geometry📐
Pythagoras' theorem, without formulas: the 3-squares proof
A right triangle, three squares drawn on its sides. The visual trick that makes the formula obvious.
- Middle school📐Geometry🖼️
Perimeter or area? Never confuse the two
Perimeter is a length (m, cm). Area is a surface (m², cm²). A simple rule to never mix them up.
- High school📐Geometry🥧
The disk area in one picture: slice it up
Slice a disk into thin points, rearrange them into a parallelogram. Its width? π·r. Its height? r. That's where π·r² comes from.
- Middle school📐Geometry≡
Two parallel lines + one transversal = equal angles
Alternate interior angles and corresponding angles: the patterns to spot to solve 90% of angle problems.
