Why dipoles of a E-field probe are slanted exactly by 54.74 degrees?

Dear all,

I am looking at a 3 dipole E-field probe which is monunted on an equilateral triangle tube. The data sheet says this is an isotropic probe and the 3 dipoles are orthogonal to each other. The dipoles are slanted at an angle of 54.74 degrees from the axis of the tube. Anyone has an ideal why all 3 dipoles slanted at this angle on a equilateral triangle tube is orthogonal to each other? Visually they do not seem to be orthogonal.

Any help will be very much appreciated.

Regards,
Element7k