the minimum length of ladder is 5.406m
answer is very simple . the length of the ladder which is to be caluclated must be minimum .
so the length of the ladder = 3*cosec (x)+sec(x)
applying derrivation on both sides gives the minimum length of ladder required
the minimumlength of the ladder is 3cosec(55.7)+sec(55.7) (in degrees)
the minimum length of the ladder is 5.406m