Question

Помогите, даю 100 балов!!!!

Answer 1

Объяснение:

= 1 + \cos \alpha - \cos \alpha - \cos^{2} \alpha + \cos^{2} \alpha = 1 \\ \\ \\ = \sin^{2} (\pi - \alpha) + (2 \ \cos^{2} - 1) = \sin^{2} \alpha + \cos2 \alpha = \sin^{2} \alpha + \cos^{2} \alpha - \sin^{2} \alpha = \cos^{2} \alpha \\