Draw any waveform and watch its frequency spectrum appear — sums of sines decompose everything
Draw on the waveform canvas, or choose a preset
Any periodic signal decomposes into a sum of sine waves (harmonics). The Fourier transform reveals the amplitude and phase of each frequency component.
The Gibbs phenomenon: reconstructing a square wave with N harmonics shows ~9% overshoot at discontinuities that persists as N → ∞.
The phasor animation shows rotating complex exponentials e2πikt/T being summed.