<span>2 cos^2 x - 3 cos x +1 = 0</span>
чтобы перевести градусы в радианы нужно использовать след формулу:
[единица в градусах] * ![\frac{\pi }{180}](https://tex.z-dn.net/?f=%5Cfrac%7B%5Cpi%20%7D%7B180%7D)
![24*\frac{3.14}{180}= 0.418\\\\240*\frac{3.14}{180}=4.18\\\\154*\frac{3.14}{180}=2.68\\\\1025*\frac{3.14}{180}=17.88\\\\2040*\frac{3.14}{180}=35.58\\\\2405*\frac{3.14}{180}=41.95](https://tex.z-dn.net/?f=24%2A%5Cfrac%7B3.14%7D%7B180%7D%3D%200.418%5C%5C%5C%5C240%2A%5Cfrac%7B3.14%7D%7B180%7D%3D4.18%5C%5C%5C%5C154%2A%5Cfrac%7B3.14%7D%7B180%7D%3D2.68%5C%5C%5C%5C1025%2A%5Cfrac%7B3.14%7D%7B180%7D%3D17.88%5C%5C%5C%5C2040%2A%5Cfrac%7B3.14%7D%7B180%7D%3D35.58%5C%5C%5C%5C2405%2A%5Cfrac%7B3.14%7D%7B180%7D%3D41.95)
2*cos²2x=1+2*sin²2x
2*cos²x-2*sin²2x=1
2*cos4x=1
cos4x=1/2
4x=+/- π/3+2πn
x=+/-π/12+2πn ⇒
x₁=π/12+2πn
x₂=-π/12+2πn.
Вот. в 7 ответ: а,б
8: 1/4; 1 1/4