The similarity sign is because we are lacking the multiplication of the derivative of the input sum in layer l. Make sure you understand this matrix ...
The m rows are horizontal and the n columns are vertical. Each element of a matrix is often denoted by a variable with two subscripts. For example, a2,1 ...
Schematic of a fully connected layer and a matrix multiplication without transfer-function applied.
Since acceleration is the time derivative of velocity, the material acceleration can be derived from the definition of material derivative as follows:
Using only direction of vector
UNIT 2: DERIVATIVES
For an alternative derivation, we can make use of the usual vector operations to express the total second derivative of the absolute position vector r.
Vector addition for vectors at any angle | Adding vectors | How to add vectors
Vector addition for perpendicular vectors | Adding vectors | How to add vectors