An incident wave is represented by `y(x,t)=20sin(2x-4t)`.
Write the expression for reflected wave (i) from a rigid boundary (ii) from an open boundary.

Explanation

To solve the problem, we need to derive the expressions for the reflected wave from both a rigid boundary and an open boundary based on the incident wave given by the equation:

\[ y(x,t) = 20 \sin(2x - 4t) \]

### Step 1: Understand the Incident Wave
The incident wave is given by:
\[ y(x,t) = 20 \sin(2x - 4t) \]
This can be rewritten to emphasize its components:
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