Sometimes, you can reorient your problem such that a matrix or tensor has only diagonal entries, making it easier to handle.
For example by choosing new unit vectors or by changing the set of functions describing the problem (whatever is the thing that the matrix or tensor is tied to).
Can someone explain with only basic algebra? I tried reading the wiki but was a bit much.
Sometimes, you can reorient your problem such that a matrix or tensor has only diagonal entries, making it easier to handle.
For example by choosing new unit vectors or by changing the set of functions describing the problem (whatever is the thing that the matrix or tensor is tied to).