## Precalculus (6th Edition) Blitzer

Step 1. Start from function $y=tan(x)$ (purple) to obtain $y=tan(\frac{x}{2})$ by stretching horizontally with a factor of 2 (new function has a period $2\pi$, and is not shown to avoid mixing with the final result). Step 2. Start from $y=tan(\frac{x}{2})$ and reflect the negative parts with respect to the x-axis to get the red curve for $y=|tan(\frac{x}{2})|$.