You would need to know the dimensions of the pyramid and wether it was triangle or square bottomed
-- If the 55° angle is one of the two equal angles, then
the third angle is 70° .
-- If the 55° angle is the third angle, then each of the two
equal angles is 62.5° .
-- For either of these cases, there are an infinite number
of possible sets of side-lengths.
The statement in the question does not hold water.
