<span>89=21х+13
89-13=21х
76=21х
х=3 целых 13/21</span>
N1
cos(x)^2 - sqrt(3)sin(x)cos(x) = 0
cos(x)(cos(x) - sqrt(3)sinx) = 0
cos(x) = 0 cos(x) - sqrt(3)sin(x) = 0
2(cos(x)/2 - sqrt(3)sin(x)/2) = 0
cos(x)/2 - sqrt(3)sin(x)/2 = 0
sin(π/6)cos(x) - cos(π/6)sin(x) = 0
sin(π/6 - x) = 0
x = π/2 + πn π/6 - x = πk
- x = -π/6 + πk
x = π/6 - πk
x = π/6 + πk
Ответ : x = π/2 + πn, x = π/6 + πk
N2
cos(x) =< -0,5
cos(x) = -0,5
x = -2π/3 + 2πn = 4π/3 + 2πn
x = 2π/3 + 2πn
cos(x) =< -0,5
x € [2π/3 + 2πn; 4π/3 + 2πn]
Ответ : [2π/3 + 2πn; 4π/3 + 2πn]
(6,1/8-1,75)÷(9-2,2×(5,6/11-3,5))×1,2/7= (6,1/8- 1,3/4):(9-2,1/5*(5,6/11-3,1/2))*1,2/7= (6 1/8-1 6/8):(9-2 1/5*(5 12/22-3 11/22))*1 2/7= 4 3/8:(9-2 1/5* 2 1/22)*1 2/7= 4 3/8:(9-11/5*45/22)*9/7= 35/8:(9-9/2)*9/7= 35/8:(18/2-9/2)*9/7= 35/8:9/2*9/7= 35/8*2/9*9/7= 35/36*9/7 = 5/4= 1 1/4