Two waves are represented by the equations $y_1 = a \sin (wt + kx + 0.57) m$ and $y_2 = a \cos (wt + kx) m, where \;$x$\; is\; in\; meter\; and\;$t in sec. The phase difference between them is :

Question

( A ) 1.25 radian
( B ) 1.57 radian
( C ) 1 radian
( D ) 0.57 radian