Triangle Inequality Applications
## Formula
$$|z_1+z_2|\le|z_1|+|z_2|$$
$$|z_1-z_2|\le|z_1|+|z_2|$$
$$|z_1+z_2+z_3|\le|z_1|+|z_2|+|z_3|$$
More generally:
$$\left|\sum_{k=1}^{n}z_k\right|\le\sum_{k=1}^{n}|z_k|$$
## Usage
- Used to find upper bounds of complex expressions.