Question

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1.sin 780 градусов
2.cos 13 п/б

Answer 1

$sin780=sin(720+60)=sin60= \frac{ \sqrt{3} }{2}$

$cos \frac{13 \pi }{6} =cos(2 \pi + \frac{ \pi }{6} )=cos \frac{ \pi }{6} = \frac{ \sqrt{3} }{2}$

Answer 2

sin 780 = sin (720 + 60) = sin (2*360 + 60) = sin(2π + 60) = sin 60 = √3/2

cos13π/6 = cos(12π/6 + π/6) = cos(2π + π/6)= cos π/6 = √3/2