In the Cartesian plane, two vectors are said to be perpendicular if the angle between them is 90, while in Cartesian space, the norm of a vector is the square root of the vector dotted with itself.
In Cartesian space, the norm of a vector is the square root of the vector dotted with itself. In the Cartesian plane, two vectors are said to be perpendicular if the angle between them is 90 (i.e. if they form a right angle). 
