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are denoted by letters in clarendon type, as E.

The three components of a vector E are denoted by Ex, Ey, Ez, and the magnitude of the vector is denoted by E, so that

$E^2 = E_x^2 + E_y^2 + E_z^2$

The vector product of two vectors E and H, which is denoted by [E.H], is the vector whose components are (EyHz - EzHy, EzHx - ExHz, ExHy - EyHx). Its direction is at right angles to the direction of E and H, its magnitude is represented by twice the area of the triangle formed by them.

The scalar product of two vectors E and H is ExHx + EyHy + EzHz. It is denoted by (E.H).

The quantity $$\frac{\partial E_x}{\partial x} + \frac{\partial E_y}{\partial y} + \frac{\partial E_z}{\partial z}$$ is denoted by div E.

The vector whose components are

is denoted by curl E.

If V denote a scalar quantity, the vector whose components are $$\left( -\frac{\partial V}{\partial x}, -\frac{\partial V}{\partial y}, -\frac{\partial V}{\partial z} \right)$$ is denoted by grad V.

The symbol ∇ is used to denote the vector operator whose components are $$\frac{\partial}{\partial x}$$, $$\frac{\partial}{\partial x}$$, $$\frac{\partial}{\partial x}$$.

Differentiation with respect to the time is frequently indicated by a dot placed over the symbol of the variable which is differentiated.