помагите СОР 8 КЛАСС АЛГЕБРА

1) 8(1-Sin²x) + 6sinx = 3
    8 - 8Sin²x + 6Sinx -3 = 0
8Sin²x -6Sinx -5 = 0
Решаем как квадратное
D = 36 -4*8*(-5) = 196
Sinx = (6+14)/16 = 20/16 ( нет решений)
Sinx =(6 -14)/16 = -1/2
Sinx = -1/2
x = (-1)^(n+1)π/6 + nπ, n ∈Z
2)Cos²2x + Cos6x -Sin²2x = 0
    Cos4x + Cos6x = 0  ( формула суммы косинусов)
2Сos5xCosx = 0
Cos5x = 0                    или               Cosx = 0
5x = π/2 + πk , k ∈Z                           x = π/2 + πn , n ∈Z  
x = π/10 + πk/5, k ∈Z
 3) (Cos²2x - Sin²2x)(Cos²2x+Sin²2x) = √3/2
Cos²2x -Sin²2x = √3/2
Cos4x = √3/2
4x = +-arcCos(√3/2) + 2πk , k ∈Z
4x = +-π/6 +2πk , k ∈Z
x = +-π/24 + πk/2 , k ∈Z
4) 4Sin²x -8SinxCosx +10Cos²x = 3*1
4Sin²x -8SinxCosx +10Cos²x = 3(Sin²x + Cos²x)
4Sin²x -8SinxCosx +10Cos²x -3sin²x - 3Cos²x = 0
Sin²x -8SinxCosx +7Cos²x = 0 | : Cos²x
tg²x - 8tgx +7 = 0
По т. Виета  tgx = 1             или            tgx = 7
                   x = π/4 + πk , k ∈Z              x = arctg7 + πn , n ∈Z   
5) 1 + Cosx + Cos2x = 0
     1 + Cosx + 2Cos²x - 1 = 0
Cosx + 2Cos²x = 0
Cosx(1 +2Cosx) = 0
Cosx = 0         или        1 + 2Cosx = 0
x = π/2 + πk , k ∈Z         Cosx = -1/2
                                        х = +-arcCos(-1/2) +2πn , n ∈Z
                                        x = +-2π/3 + 2πn , n ∈Z  
6) -Cosx > -0,5
     Cosx < 0,5
-π/3 + 2πk < x < π/3 + 2πk , k ∈Z

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Social Studies

5 points

Question from Egor9klass

Why civil

society in developed countries

formed only in

the last two centuries?

Answer

VERIFIED RESPONSE

Account deleted •

Civil

society is possible only under legal conditions

(democratic)

states. That's why it

formed in developed countries only in

the last two centuries, since before

this was the case in an authoritarian and totalitarian way

mode in which

civil society is functioning normally

can't.

4.0 (64)

COMMENT

estimate

thanks

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