Why do we bother to learn Tensor? Einstein may shout loud that it’s a must after he came up with Special Relativity Theory, setting foot for General Relativity, a daunting, seemingly invincible obstacle is math in 4-dimensional space that converts. Tensor is a great tool to make it so easy.

For example, grasped the Jacobian matrix as the transforming vehicle,

It’s easy to conclude that these two are same objects – invariant object.