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Explore Stoic logic through its five indemonstrables, connectives, implication, excluded middle, and the temporal nature of truth.
Explore Euclidean isometries through rational trigonometry, deriving projection and reflection formulas and connecting line reflections to the Weierstrass substitution.
Explore a rational formulation of plane rotations connecting the Euclidean rotation group with complex number multiplication and half-slopes on the unit circle.
An algebraic treatment of isometry groups, reflections, and rotations across Euclidean and relativistic planar geometries without angles or transcendental functions.
Examines why radian measure is used, tracing its dependence on calculus and challenging the usual high-school justification.
Explore the historical and conceptual role of circular functions, from uniform motion around a circle to the choice of natural and angular units.
Explore how Rheticus’s 17th-century trigonometric tables shaped classical trigonometry through double-, half-, and triple-angle formulas.
Derive the general laws of rational trigonometry algebraically using quadrance, spread, and a bilinear form.
Explore rational trigonometry with an arbitrary symmetric-matrix dot product, extending quadrance, perpendicularity, and spread to a geometry whose unit circle may appear as an ellipse.
Learn how modular arithmetic and congruences simplify remainders, divisibility tests, and calculations involving powers of 10.
A brief overview of ancient Indian contributions to astronomy and related trigonometry, including trigonometric sign tables and the work of Brahma Gupta.
Explore divisibility of natural numbers using long division, repeated subtraction, and modular arguments for large-number problems.
Explore how Babylonian and other ancient observers understood the night sky through the celestial sphere, great circles, equatorial coordinates, and angular measurements.
Explores Petrie polygons of Platonic solids, regular tessellations, and their behavior under perspective and orthogonal projection.
Explore the rotational symmetries of Platonic solids through rigid motions, directed edges, and the duality of cubes and octahedra.
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