# Coordinate system handedness

1. Sep 9, 2012

### 1MileCrash

How do you define a right handed coordinate system for a basis which is not orthonormal?

2. Sep 10, 2012

### voko

When you use the right hand rule and actually try to do that with your hand, you almost always get a non-orthonormal basis. If the angles between you fingers are very oblique, that is a good example; non of the angles may be zero, however.

More formally, it should be any three vectors not pairwise collinear, and forming a right-hand triad.

3. Sep 10, 2012

### 1MileCrash

Book just says scalar triple product positive for right hand, negative for left...

4. Sep 10, 2012

### voko

Yeah, it boils down to that. One caveat is that it depends on the definition of the vector product, which itself includes right-handedness.

5. Sep 10, 2012

### 1MileCrash

That's interesting.. so really, if it is negative it means it "differs" from the way we have defined the vector product (right handed.)

Thanks.

6. Sep 11, 2012

### chiro

It basically boils down to a positive determinant of the all the basis vectors in their natural order. If it's positive then it's right handed, if it's negative it's left handed (you can't get zero and if you do it means you've done something wrong).

I Coordinate systems in $\mathbb{R}^2$ Yesterday at 8:51 AM