#curves

• Antipedal curve — A plane geometric curve or derived figure obtained as the locus of the feet of perpendiculars drawn from a fixed point (called a pole) onto the normals of a given curve; also, it can define a structural property related to podal curves in higher analytical geometry. This concept is used in studying kinematic properties and complex geometric transformations of lines.
• Antipolar line — A straight line or derived geometric curve associated with a fixed point (called a pole) within a dual geometric transformation based on inversion, having contrary or symmetrical properties relative to a classical polar line. This structural element is used in higher projective geometry to study inverse polar coordinate systems and the tangency properties of conics.
• Harmonograph — A mechanical apparatus or device consisting of a system of oscillating pendulums, used to draw and graphically visualize complex geometric curves resulting from the combination of two or more sinusoidal harmonic or vibratory motions.
• Astrophotometry — A fundamental branch of practical astrophysics that deals with measuring the intensity, flux, and brightness of radiant energy (light) emitted by celestial bodies across different bands of the electromagnetic spectrum. Data obtained through astrophotometry (using photometers or CCD sensors) allow astronomers to determine cosmic distances, surface temperatures, rotational periods of variable stars, and to detect exoplanets via the transit method.