Question

8√3cos²(7π/12) - 8√3sin²(7π/12) =?​

Answer 1

Ответ:

-12

Объяснение:

8√3cos²(7π/12) - 8√3sin²(7π/12) = 8√3[cos²(7π/12) - sin²(7π/12)]=

= 8√3*[cos(2*7π/12)] = 8√3cos(7π/6) = 8√3cos(π+π/6) =

= 8√3*(-cos(π/6)) = 8√3*(-√3/2) = -4*3 = -12

*** Применялись формулы:

1) cos²a-sin²a = cos2a

2) cos (π+a) = -cosπ