[Math] Linear Algebra: Orthogonal and perpendicular

linear algebra

Simple and quick question. These two have to do with 90 degree angles.

This is the picture of the two words I have.

Perpendicular is strictly restricted to lines.

  • "Line A and B are perpendicular to each other."

  • "v=(1, 1) and w=(-1, 1) -> cv and dw are perpendicular towards each other."

Orthogonal is restricted to matrices.

1  1  1  1   
1 -1  1 -1  
1  1 -1 -1   
1 -1 -1  1
  • The above matrix is an orthogonal matrix.

So would be following statement be correct: A orthogonal matrix has vectors which are perpendicular towards each other?

Best Answer

Usually the term "orthogonal matrix" is reserved for matrices whose columns are not only mutually perpendicular, but also unit vectors. So if you were to divide each entry in your matrix above by $2$, it would be an orthogonal matrix.

There appears to be no standard term for a matrix whose columns are just orthogonal without any restriction on their norms.