1) cos 780
cos(780) = cos(720 + 60)= cos(720)cos(60) - sin(720)sin(60)= cos(60) - sin(720)sin(60) (cos(720) = -1, sin(720) = 0)= 1/2
Ответ: cos 780 = 1/2
2) sin(13/6)
sin(13/6) = sin(2π + π/6)= sin(2π)cos(π/6) + cos(2π)sin(π/6)= 0 √3/2 + 1 1/2= 1/2
Ответ: sin(13/6) = 1/2
1) cos 780
cos(780) = cos(720 + 60)
= cos(720)cos(60) - sin(720)sin(60)
= cos(60) - sin(720)sin(60) (cos(720) = -1, sin(720) = 0)
= 1/2
Ответ: cos 780 = 1/2
2) sin(13/6)
sin(13/6) = sin(2π + π/6)
= sin(2π)cos(π/6) + cos(2π)sin(π/6)
= 0 √3/2 + 1 1/2
= 1/2
Ответ: sin(13/6) = 1/2