find the sum of coefficient in `(x+y)^(8)`.

Answer

To find the sum of the coefficients in the expression \((x+y)^{8}\), we can follow these steps:

### Step 1: Understand the Expression
The expression \((x+y)^{8}\) represents a polynomial. The coefficients of this polynomial are the numbers that multiply the terms when the polynomial is expanded.

### Step 2: Substitute \(x\) and \(y\) with 1
To find the sum of the coefficients, we can substitute \(x = 1\) and \(y = 1\) into the expression. This is because substituting 1 for both variables will add all the coefficients together.

\[ (1 + 1)^{8} \]

### Step 3: Simplify the Expression
Now we simplify the expression:

\[ (1 + 1)^{8} = 2^{8} \]

### Step 4: Calculate \(2^{8}\)
Next, we calculate \(2^{8}\):

\[ 2^{8} = 256 \]

### Final Answer
Thus, the sum of the coefficients in \((x+y)^{8}\) is:

\[ \boxed{256} \]