The Pythagorean modes (there are three of them) can be used to indirectly measure places that are either hard to access or difficult to measure directly with the meter. It’s based on the fact that measuring two sides of a right triangle allows you to calculate the length of the third side. For example: you can measure the height of a building by making one horizontal measurement close to the ground, and another one at an angle to the top edge of the building. The meter then calculates and displays the height of the building from your two measurements. To learn more about the different Pythagorean modes, check out the user manual, it explains these and other modes like “Area” and “Volume” in detail.