### 90° angles

The angle most often used in the trades is the 90° angle.

It may help to understand why this is so.

When two straight lines cross, four angles are created.

Those four angles always add up to 360° .

The major lines of the compass are two straight

lines which cross each other at 90° angles.

Most plants and factories are said to be built along

the major lines of the compass.

When lines cross, the only time all four of the angles

created are equal to each other is when each angle is

a 90° angle. A 90° angle is called a right angle.