Sin3x +sinx =2sin(3x+x)/2*cos(3x-x)/2 =2sin2x*cosx.
sinx -sin3x =2sin(x-3x)/2*cos(x+3x)/2 =2sin(-x)*cos2x = -2sinx*cos2x.
cos5y +cosy =2cos(5y+y)/2*cos(5y -y)/2 =2cos3y*cos2y.
cos4z+cos2z =2cos3z*cosz.
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sinx -sin3x =sinx +sin(-3x) =2sin(x+(-3x))/2*cos(x-(-3x))/2 =2sin(-x)*cos2x = -2sinx*cos2x.
6+3+4=13,6+4=10,отношение 10/13=0,8
1. D=36
x=(4+-6)/2=5; -1
Ответ: -1; 5
2. D=100+44=144
x=(10+-12)/2=11; -1
Ответ: -1; 11
1) 6(-3n-2m)
2) 6(x+4)
3) 3(3+4y)
4) 4a(y-2)
sin117=sin(90+27)=cos27
cos153=cos(180-27)=-cos27
cos270=0
cos27-3cos27+0=-2cos27
-2cos27/cos27 = -2
Ответ: -2