Evaluate: `int(sinx)/(cos^2x)\ dx`

Explanation

To evaluate the integral \( I = \int \frac{\sin x}{\cos^2 x} \, dx \), we will use substitution and trigonometric identities. Let's go through the solution step by step.

### Step 1: Rewrite the Integral
We start with the integral:
\[ I = \int \frac{\sin x}{\cos^2 x} \, dx \]
We can rewrite \(\frac{\sin x}{\cos^2 x}\) as \(\sin x \cdot \sec^2 x\).
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