Answer
$$\sin(\csc t)=1$$
Take $t=\frac{\pi}{2}$, which meaks $\sin(\csc t)\ne1$. Therefore, the equation cannot be an identity.
Work Step by Step
$$\sin(\csc t)=1$$
To show an equation to not be an identity, we only need to find one example in which 2 sides are unequal.
Here we can take $t=\frac{\pi}{2}$, but remember that there are other choices as well.
$$\csc t=\csc\frac{\pi}{2}=1$$
Therefore, $$\sin(\csc t)=\sin1\approx0.841\ne1$$ (remember that $1$ here is in radian)
Thus at $t=1$, 2 sides are not equal. The equation, therefore, cannot be an identity.
