`e^(6x)"cos"3x`

Explanation

To find the second order derivative of the function \( y = e^{6x} \cos(3x) \), we will follow these steps:

### Step 1: Differentiate the function to find the first derivative \( \frac{dy}{dx} \)

We will use the product rule for differentiation, which states that if \( y = u \cdot v \), then \( \frac{dy}{dx} = u'v + uv' \).

Let:
- \( u = e^{6x} \) and \( v = \cos(3x) \)
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