Concept
Sine
2 essays name this object, across one field. What follows is each of them, and the objects they name alongside it.
A sine wave is a circle seen from the side
Sine is introduced as a ratio in a right triangle, which is true and explains nothing about why its graph is a wave. There is a better picture.
A square wave built entirely out of round ones
Add enough sine waves together and flat tops and vertical cliffs appear from nothing. Almost — there is a 9% overshoot that never goes away, and it is not a bug.
Named alongside it
The objects these essays reach for when they reach for this one.
PeriodicityPiContinuityConvergenceCosineDerivativeGibbs' phenomenonHarmonicsOrthogonalityRadianSimple harmonic motionSpectrum