Principle of superposition:
The net electric field at any point is equal to the vector sum of the respective electric fields that each charge distribution would create on its own.
\boxed{\overrightarrow{E}_{net}=\overrightarrow{E}_{1}+\overrightarrow{E}_{2}+\overrightarrow{E}_{3}+\dots}
Example:
The net electric field ${\overrightarrow{E}}_{net}$ at point $P$ is equal to the vector sum of the individual electric fields ${\overrightarrow{E}}_1$ and ${\overrightarrow{E}}_2$ created by point charges $q_1$ and $q_2$ respectively. Thus, we write
\boxed{{\overrightarrow{E}}_{net}={\overrightarrow{E}}_1+{\overrightarrow{E}}_2}
In practice, since the above equation is the sum of two vectors, we write it in component form as follows
\begin{aligned} {\overrightarrow{E}}_{net}={\overrightarrow{E}}_1+{\overrightarrow{E}}_2\ \ \ \ &\Rightarrow \ \ \ \ \ \left\{ \begin{array}{c} E_{net\ x}=E_{1x}+E_{2x} \\ E_{net\ y}=E_{1y}+E_{2y} \end{array} \right. \\ \\ &\Rightarrow \ \ \ \ \ \left\{ \begin{array}{c} E_{net\ x}=E_1{\mathrm{cos} \left({\theta }_1\right)\ }+E_2{\mathrm{cos} \left({\theta }_2\right)\ } \\ E_{net\ y}=E_1{\mathrm{sin} \left({\theta }_1\right)\ }-E_2{\mathrm{sin} \left({\theta }_2\right)\ } \end{array} \right. \end{aligned}
The magnitude of the net electric field at point $P$ is therefore equal to
E_{net}=\sqrt{E^2_{net\ x}+E^2_{net\ y}}=\sqrt{{\left(E_1{\mathrm{cos} \left({\theta }_1\right)\ }+E_2{\mathrm{cos} \left({\theta }_2\right)\ }\right)}^2+{\left(E_1{\mathrm{sin} \left({\theta }_1\right)\ }-E_2{\mathrm{sin} \left({\theta }_2\right)\ }\right)}^2}