Answer:
The equation for such type of wave is
![D_2 = sin(0.84.x + 47t + 21)](https://img.qammunity.org/2021/formulas/physics/college/sm3nel5bznrxz5mk4p1e7yy5h1teg8eyk8.png)
Step-by-step explanation:
From the question we are told that
The displacement is
![D_1 = 4.2sin(0.84.x - 47t + 21)](https://img.qammunity.org/2021/formulas/physics/college/f08pgrb4x0mzhp8ajn5rf9d74xxz348hut.png)
Here the wave number is k= 0.84
The angular frequency is
![w = 47](https://img.qammunity.org/2021/formulas/physics/college/wi085kfozczpqzgsha42az3l8fy7j58bgv.png)
The phase shift is
![\phi = 21](https://img.qammunity.org/2021/formulas/physics/college/wpnzldl0m9rvvwtswnlh3fasvlh5djlugv.png)
Generally the equation that represents a wave which, when traveling in the opposite direction, will produce a standing wave when added to this one is mathematically represented as
![D_2 = sin(0.84.x + 47t + 21)](https://img.qammunity.org/2021/formulas/physics/college/sm3nel5bznrxz5mk4p1e7yy5h1teg8eyk8.png)