Question

Electric field at a point due to an electric dipole on an axis inclined at an angle theta <90° to the dipole axis is perpendicular to the dipole axis if the angle theta is

Answer 1

its not tan alpha (90 - theta )

its tan( 90 - theta )

from the fig

using angle sum property of triangle

90+alpha + theta = 180

alpha = 90 - theta

which gives

tan alpha = tan (90 - theta ) = cot theta = 1 / tan theta