sinx+cos2x+sin2x+cosx=0 giải pt

1 bình luận về “sinx+cos2x+sin2x+cosx=0 giải pt”

1. sinx+cos2x+sin2x+cosx=0

   <=> 1/sqrt(2)sinx + 1/sqrt(2)cosx + 1/sqrt(2)sin2x + 1/sqrt(2)cos2x = 0

   <=> sin(x+pi/4)+sin(2x+pi/4) = 0

   <=> sin(x+pi/4) = -sin(2x+pi/4)

   <=> sin(x+pi/4) = sin(-2x-pi/4)

   <=> [(x + pi/4 = -2x-pi/4+k2pi),(x + pi/4 = pi + 2x +pi/4 +k2pi):}

   <=> [(x = -pi/6+(k2pi)/3),(x= -pi – k2pi):}(kinZZ)

    

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