I think both the followings are different -
- prove that $(p\Leftrightarrow q)\rightarrow (p\rightarrow \sim q)$ is a tautology.
- prove that $(p\Leftrightarrow q)\rightarrow (p\rightarrow \sim q)$.
In 1st one if you show a combination of p,q such that LHS is T & RHS is F, you can declare that this is not a tautology.
In 2nd one you have to check whether LHS implies RHS or not, i.e you've to check whether this follows the implication rule(means truth table) or not.
Now according to the qsn. language, it feels like they want the 2nd one, not the 1st one.