The trapezoid area formula is A = ½(b₁ + b₂)h, where b₁ and b₂ are the parallel sides…
Solve any triangle from 3 given parts: SSS, SAS, ASA, AAS, and the SSA ambiguous case. Step-by-step examples…
When does the quadratic formula appear in geometry? Find circle-line intersections, work backwards from area to side length,…
Master the two-column proof: statements on the left, reasons on the right. Postulates and theorems cheat list, a…
Solve for x in any geometry problem: angle sums, similar triangles, Pythagoras, area formulas, parallel lines, vertical angles.…
Every 3D solid formula in one place: cube, rectangular prism, cylinder, sphere, cone, pyramid. Volume + surface area…
Master the distance formula d = √((x₂−x₁)²+(y₂−y₁)²) and midpoint M = ((x₁+x₂)/2, (y₁+y₂)/2). Full derivation, worked examples, and…
Geometric sequence formula aₙ = a·rⁿ⁻¹ vs series Sₙ = a(1−rⁿ)/(1−r). When does the infinite sum converge? Worked…
Polygon angle formulas: interior sum (n−2)×180°, exterior sum 360° always, plus each angle for regular polygons. Worked examples…
Ten Pythagorean theorem examples from basic right-triangle leg-finding to applied 3D distance and Pythagorean triples. Each with full…