Question

(cos75°-sin75°)∙( sin75°+ cos75°) помогите

Answer 1

$(cos75^0-sin75^o)*( sin75^o+ cos75^o) = cos^275^o - sin^275^ o=\ \ = frac{1+cos2*75}{2}-frac{1-cos2*75}{2} = frac{1+cos150 - 1 + cos150}{2} = \ \ =frac{2 * cos150}{2} = cos150 = cos(180 - 30) = cos 30 = frac{sqrt{3}}{2}$