Answer :

To verify the trigonometric identity
[tex]\[ \sec \theta - \cos \theta = \tan \theta \sin \theta, \][/tex]
we will simplify both sides of the equation and show that they are indeed equal.

Firstly, recall the definitions of the trigonometric functions involved:
[tex]\[ \sec \theta = \frac{1}{\cos \theta}, \][/tex]
[tex]\[ \tan \theta = \frac{\sin \theta}{\cos \theta}. \][/tex]

### Left-Hand Side (LHS)

Consider the left-hand side of the identity:
[tex]\[ \sec \theta - \cos \theta. \][/tex]

Substitute \(\sec \theta\) with \(\frac{1}{\cos \theta}\):
[tex]\[ \frac{1}{\cos \theta} - \cos \theta. \][/tex]

To combine the terms, we need a common denominator:
[tex]\[ \frac{1 - \cos^2 \theta}{\cos \theta}. \][/tex]

Using the Pythagorean identity, \(1 - \cos^2 \theta = \sin^2 \theta\), we rewrite the expression as:
[tex]\[ \frac{\sin^2 \theta}{\cos \theta}. \][/tex]

### Right-Hand Side (RHS)

Now, consider the right-hand side of the identity:
[tex]\[ \tan \theta \sin \theta. \][/tex]

Using \(\tan \theta = \frac{\sin \theta}{\cos \theta}\), substitute it into the expression:
[tex]\[ \left(\frac{\sin \theta}{\cos \theta}\right) \sin \theta. \][/tex]

This simplifies to:
[tex]\[ \frac{\sin^2 \theta}{\cos \theta}. \][/tex]

### Compare Both Sides

We have:
[tex]\[ \text{LHS} = \frac{\sin^2 \theta}{\cos \theta} \][/tex]
and
[tex]\[ \text{RHS} = \frac{\sin^2 \theta}{\cos \theta}. \][/tex]

Since both sides simplify to the same expression, we have verified that:

[tex]\[ \sec \theta - \cos \theta = \tan \theta \sin \theta. \][/tex]

Thus, the identity is verified.

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