Remember that a difference of two squares has a special factoring pattern.
$a^2−b^2=\left(a−b\right)\left(a+b\right)$.

$\left(x + 2\right)\left(x − 2\right)$

Use the same method as part (a).

This might look different than the expressions in parts (a) and (b), but you can use the same method to factor it.

$\left(1 − x\right)\left(1 + x\right)$

Think of $\sin^2(x)$ as one big variable (like $x^2$).
Then use the same method as part (c) to factor it.