Two charge `+Q` each are placed at the two vertices of an equilateral triangle of side `a` .The intensity of electric field at the third vertex is

Explanation

`E^(1)=sqrt(E^(2)+E^(2)+2xxExxExxcos theta)`
`=sqrt(2E^(2)+2E^(2)cos theta)`
`=sqrt(2E^(2)(1+cos theta))`
`=2E cos (theta)/2, E=sqrt(3)1/(4 pi epsilon_(0)) Q/(a^(2))`