Three equal charges, each +q, are placed on the corners of an equilateral triangle. The electric field intensity at the centroid of the triangle is

$$\begin{gathered} E_{net 1}=2E\cos \frac{\theta }{2}=2E\cos \frac{120}{2}=2E\cos 60=E upwards \\ {E}_{net 2}=E downwards \\ {E}_{net }=E-E=0 \end{gathered}$$

Each charge will produce the same magnitude of intensity, say E, at the centroid. These are directed at angles of 120⁰ with each other. So, their vector sum will be zero.