Finding the Angle Between Two Intersecting Planes using the Dot Product of their Normal Vectors

In this video I show that we can determine the angle between two intersecting planes by computing the dot product of their normal or perpendicular vectors.

This follows from the dot product formula being equal to their lengths multiplied by the cosine of the angle between them.

If the planes are parallel then the angle between them will be zero, hence the cosine of the angle will be just 1.