ANSWER:
1st option:
[tex]\sin ^2x-2\sin x\cos x+\cos ^2x[/tex]
STEP-BY-STEP EXPLANATION:
We have the following expression:
[tex]\mleft(\sin x-\cos x\mright)^2[/tex]
In this case, the square of the subtraction is applied as if it were two algebraic terms, like this:
[tex]\begin{gathered} (a-b)^2=a^2-2ab+b^2 \\ \text{ in this case} \\ (\sin x\: -\: \cos \: x)^2=\sin ^2x-2\cdot\sin x\cdot\cos x+\cos ^2x \end{gathered}[/tex]
Which means the answer is:
[tex]\sin ^2x-2\sin x\cos x+\cos ^2x[/tex]
