помогите с алгеброй
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1) =sin(α -β) - cosα*(-sinβ) = (sinαcosβ -cosα*sinβ) +cosα*sinβ = sinαcosβ .
2) = (-cosα)² - (sinα)² =cos²α - sin²α = cos2α.
3) =2sinαcosβ +(cosαcosβ -sinαsinβ) =cosαcosβ+ sinαsinβ =cos(α - β) .