Ответ:

типа того

Объяснение:

Verified answer

[tex]\displaystyle\bf\\1)\\\\Cos^{2} (\pi -\alpha )+Sin^{2} (\alpha -\pi )=Cos^{2} \alpha +Sin^{2}\alpha =1\\\\\\2)\\\\Cos(\pi -\alpha )Cos(3\pi -\alpha )-Sin(\alpha -\pi )Sin(\alpha -3\pi )=\\\\=-Cos\alpha \cdot(-Cos\alpha )-(-Sin\alpha) \cdot(-Sin\alpha )=\\\\=Cos^{2} \alpha -Sin^{2} \alpha =Cos2\alpha[/tex]