X -в перв рук (x-60) во втор
(x-60)*0.8-x*0.6=12
0.8x-0.6x=12+48
0.2x=60
x=300 в пер рук
300-60=240 во втор
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Sin (7П/12) * Cos (7П/12) = 1/2 * 2 *Sin(7П/12)Cos(7П712) = 1/2 Sin(7П/6) =
= 1/2 Sin(П + П/6) = - 1/2SinП/6 = - 1/2 * 1/2 = - 1/4 = - 0,25
Cos2x+cos²x=0
2cos²x-1+cos²x=0
3cos²x=1
cos²x= 1/3
cosx= 1/√3 cosx=-1/√3
x1=+ - arccos(1/√3)+2πn, n ∈ Z
x2=+ - arccos(-1/√3)+2πn, n ∈ Z
2) sin2x=cos²x
2sinx*cosx-cos²x=0
cosx(2sinx-cosx)=0
cosx=0
x=π/2+πn, n ∈ Z
2sinx-cosx=0
2tgx=1
tgx=1/2
x=arctg1/2 + πn, n ∈ Z
3) sin2x-3cosx=0
2sinx*cosx-3cosx=0
cosx(2sinx-3)
cosx=0
x=π/2+πn, n ∈ Z
4) 2 cos²x=1+4sin2x
4 x>2-5
4x> - 3
x> -3:4
x> -0,75
( -0,75 ; + бесконечность)