solve this equation?

Question

y=6cos(5t-0.009x+0.4) find the distance between two consecutive crest.find the phase difference at two points separated by a distance of (a) 0.2m (b)

Answer 1

note that 2pie f=angular frequency (w)=5
k=0.009,or 2 pie/ lambada=0.009
distance betn 2 cosq. crests is wavelength
to find phase difference u put x as 0 in one and 0.2 in othr and u will get phase difference as (0.4-0.0018). ...if ur values r all in S.I.

Answer 2

You can not solve an equation with three unknowns.Please recheck the question.