Travelling Wave Model Question?

Question

Consider the sinusoidal wave function:
y= 15cous (.157x-50.3t)

At a certain instant let point A be at the origin snf point B be the first point along the x axis where the wave is 60.0 out of hase with A. What is the coordinate of B?

Please help me with this question, by showing the steps to find the answer.

Thanks in advance.

sorry I made a mistake, cous = cos

Answer 1

♥ thus y=15cos(x*pi/20 - 50.3*t);
let this “certain instant” for A be at t=t0=0, and x=x0=0;
then y(0,0)=15*1 =15;
♠ and for B it should look like
y(x1,t1)=15cos(x1*pi/20 - 50.3*t1) =15*cos(pi/3);
Since it is the same time t1=t0=0,
then x1*pi/20=pi/3, hence x1=20/3;