Answer
$$\sin^2\theta(1+\cot^2\theta)-1=0$$
The trigonometric expression is an identity.
Work Step by Step
$$\sin^2\theta(1+\cot^2\theta)-1=0$$
The left side would be simplified, since it is more complex.
$$A=\sin^2\theta(1+\cot^2\theta)-1$$
From a Pythagorean Identity: $$1+\cot^2\theta=\csc^2\theta$$
Also, from a Reciprocal Identity: $$\csc\theta=\frac{1}{\sin\theta}$$
Therefore, $$1+\cot^2\theta=\Big(\frac{1}{\sin\theta}\Big)^2=\frac{1}{\sin^2\theta}$$
Apply back to $A$, we have:
$$A=\sin^2\theta\times\frac{1}{\sin^2\theta}-1$$
$$A=1-1=0$$
The left side equals the right side, so it is an identity.