Verify whether the following is a trig identity:
\[
\frac{1}{\sec (\theta)} \circ \tan (\theta)=\sin (\theta)
\]

Step 1 ：Given the expression \(\frac{1}{\sec (\theta)} \circ \tan (\theta)=\sin (\theta)\), we need to verify whether it is a trigonometric identity.

Step 2 ：The secant function, \(\sec(\theta)\), is the reciprocal of the cosine function, \(\cos(\theta)\). So, \(\frac{1}{\sec(\theta)}\) is equivalent to \(\cos(\theta)\).

Step 3 ：The tangent function, \(\tan(\theta)\), is the ratio of the sine function, \(\sin(\theta)\), to the cosine function, \(\cos(\theta)\).

Step 4 ：So, the left-hand side of the equation simplifies to \(\cos(\theta) \cdot \frac{\sin(\theta)}{\cos(\theta)}\), which simplifies further to \(\sin(\theta)\).

Step 5 ：Since the left-hand side equals the right-hand side, we can conclude that \(\frac{1}{\sec (\theta)} \circ \tan (\theta)=\sin (\theta)\) is a valid trigonometric identity.

Step 6 ：Final Answer: \(\boxed{\frac{1}{\sec (\theta)} \circ \tan (\theta)=\sin (\theta)}\) is a valid trigonometric identity.