Equilateral Triangles: The Perfect Triangle Explained
Equilateral triangle: three equal sides, three 60° angles. Height (√3/2)s, area (√3/4)s², the 30-60-90 link, a table of common sizes and worked problems.
Formulas, proofs and theory behind trigonometry and geometry: the Pythagorean theorem, Law of Sines, special right triangles and triangle area formulas.
10 articles
Equilateral triangle: three equal sides, three 60° angles. Height (√3/2)s, area (√3/4)s², the 30-60-90 link, a table of common sizes and worked problems.
The Law of Sines, a/sin A = b/sin B = c/sin C, solves non-right triangles in AAS, ASA and SSA cases. When to use it, worked examples, the ambiguous case.
Perpendicular lines and area: the height in ½ × base × height must meet the base at 90°. Why, how to find it in any triangle, and measuring examples.
Triangle area formulas compared: Heron's formula for three sides, ½ab sin C, base × height, coordinates and the 3D cross product, and when each one fits.
Acute, right and obtuse triangles: tell them apart with the a² + b² vs c² test, and see which formulas (SOH-CAH-TOA, Law of Cosines, Heron's) fit each.
The unit circle explained through right triangles: with a hypotenuse of 1, sine is the y-coordinate and cosine the x-coordinate, for any angle.
30-60-90 and 45-45-90 triangles: side ratios 1 : √3 : 2 and 1 : 1 : √2, why they hold, how to remember them, and worked examples with answers.
Degrees vs radians: 180° = π radians, so multiply by π/180 to get radians and by 180/π to get degrees. Conversion table, when to use each, common mistakes.
Pythagorean triples are right triangles with whole-number sides, like 3-4-5 and 5-12-13. A list of common triples, Euclid's formula, scaling and patterns.
The Pythagorean theorem a² + b² = c² explained: what it says, why it holds only with a right angle, its history from Babylon to Euclid, and three proofs.