Question

Theoretical: Two waves are originally in phase. If one of the waves is shifted by 4 (pi) radians, the waves will now be completely out of phase. True or false? Explain if you can please

Answer 1

i would say false cause if you shift it by 4 pi rad you put it again in phase:
http://www.chemtutor.com/images/scheme.gif
as you see 2 pi gives 360 sin rad and if you shift one wave by 4 pi you basicaly just shift its phase but they are in phase