Differentiate the following w.r.t x
cos 3x

Explanation

To differentiate the function \( \cos(3x) \) with respect to \( x \), we will use the chain rule. Here’s a step-by-step solution:

### Step 1: Identify the function to differentiate
We need to differentiate \( y = \cos(3x) \).

### Step 2: Apply the chain rule
The chain rule states that if you have a composite function \( y = f(g(x)) \), then the derivative \( \frac{dy}{dx} \) can be found using:
\[
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