Which NOT listed as a current shape?

• A. Cosine
• B. Sine
• C. Triangular
• D. Spike

Answer: (A)

The main idea here is how current shapes are described in electrotherapy. Clinicians distinguish waveforms by how the current’s amplitude changes over time, and several distinct shapes are commonly used: a smooth, periodic waveform (sine), a ramped-up and down form (triangular), and short, sharp bursts (spike). A cosine wave isn’t treated as a separate current shape in this context because it is mathematically the same as a sine wave, just shifted in time. In other words, a cosine is essentially a sine with a phase shift, so it isn’t listed as a distinct shape for practical purposes.

That’s why cosine is not listed as a current shape. The other options—sine, triangular, and spike—are recognized, separate shapes that describe how the current rises and falls over time.