Three equal positive charges $q$ are at the corners of an equilateral triangle of side $a$, as shown in Figure P23.17.
(a) Assume that the three charges together create an electric field. Find the location of a point (other than $\infty$ ) where the electric field is zero. (Hint: Sketch the field lines in the plane of the charges.) (b) What are the magnitude and direction of the electric field at $P$ due to the two charges at the base?