Help_______________ sin2x+cos3x=0

1 Январь 0001



Help

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sin2x+cos3x=0

  • sin2x + cos(x+2x) = 0

    sin2x + cosx*cos2x – sinx*sin2x = 0

    sin2x - sinx*sin2x + cosx*cos2x = 0

    sin2x*(1-sinx) + cosx*(1-2(sinx)^2) = 0

    2sinx*cosx*(1-sinx) + cosx*(1-2(sinx)^2) = 0

    cosx*(2sinx*(1-sinx) + 1-2(sinx)^2) = 0

    cosx*(2sinx – 2(sinx)^2 + 1-2(sinx)^2) = 0

    cosx*(2sinx – 4(sinx)^2 + 1) = 0

    cosx = 0 или 2sinx – 4(sinx)^2 + 1

    4(sinx)^2 – 2sinx – 1 = 0 D = 4 + 4*4 = 20

    sinx = (2-2V5)/8 = (1 – V5)/4

    sinx = (2+2V5)/8 = (1 + V5)/4

    ——————————————-

    x = pi/2 + k*pi

    x = (-1)^k * arcsin((1 +- V5)/4) + k*pi

    как-то так…







Алгебра

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