Answer:
Civil Engineer.
Step-by-step explanation:
There are plenty profession that used this concept, but Civil Engineer has to seriously rely on this concept, because life depend on it.
A Civil Engineer is like an architect but works in the field, making structural analysis of the buildings, continuously. Their knowledge is mainly math, specifically geometry, because they need to set balancing forces, in order to get stabilisation in buildings, where perpendicular and parallel lines are often included, due to the complexity of the matter.