Question

(/3/2+cos альфа.....
$\frac{ \sqrt{3} }{2} + \cos( \alpha )$
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Answer 1

Ответ:

$\displaystyle -0,5+\frac{\sqrt{2} }{4}$

Объяснение:

запишите в виде суммы:  $\displaystyle cos\frac{\pi }{4} *cos\frac{\pi }{12}$

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$\displaystyle cos\frac{\pi }{4} *cos\frac{\pi }{12}=cos\frac{180^\circ}{4} *cos\frac{180^\circ}{12} =cos45^\circ*cos15^\circ=\frac{\sqrt{2} }{2} *cos(135^\circ-120^\circ)=\frac{\sqrt{2} }{2} \bigg(-\frac{\sqrt{2}}{2} -\bigg(-\frac{1}{2} \bigg)\bigg)=\frac{\sqrt{2} }{2} \bigg(-\frac{\sqrt{2} }{2} +\frac{1}{2} \bigg)=-\frac{2}{4} +\frac{\sqrt{2} }{4} =-0,5+\frac{\sqrt{2} }{4}$