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Solve: x (dy/dx) -2yx^3 cos(x) y(pi/2)=1

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Answer to a math question Solve: x (dy/dx) -2yx^3 cos(x) y(pi/2)=1

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Sigrid
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115 Answers
Para resolver esta ecuación diferencial, primero hallamos la ecuación diferencial dada:
x\frac{dy}{dx} - 2yx^3\cos(x)

Luego, debemos separar las variables y resolver la ecuación diferencial:

\frac{dy}{y} = \frac{2x^3\cos(x)dx}{x}

Integrando ambos lados obtenemos:

\int \frac{dy}{y} = \int 2x^2\cos(x)dx

Resolviendo las integrales:

\ln|y| = 2\int x^2\cos(x)dx

Usando integración por partes en la integral de la derecha, con u = x^2 y dv = \cos(x)dx, entonces du = 2xdx y v = \sin(x):

\ln|y| = 2(x^2\sin(x) - 2\int x\sin(x)dx)

Integrando nuevamente por partes, con u = x y dv = \sin(x)dx, entonces du = dx y v = -\cos(x):

\ln|y| = 2(x^2\sin(x) + 2x\cos(x) + 2\cos(x)) + C

Simplificando y tomando exponencial en ambos lados para eliminar el logaritmo:

y = e^{2(x^2\sin(x) + 2x\cos(x) + 2\cos(x) + C)}

Finalmente, dado el dato inicial y\left(\frac{\pi}{2}\right) = 1, podemos encontrar la constante C:

1 = e^{2\left(\frac{\pi^2}{4} - 2 + 2\right) + C} = e^{\frac{\pi^2}{2} - 4 + 2 + C} = e^{\frac{\pi^2}{2} - 2 + C}

Por lo tanto, la solución a la ecuación diferencial dada con la condición inicial es:

y = e^{2(x^2\sin(x) + 2x\cos(x) + 2\cos(x) + \frac{\pi^2}{2} - 2)}

\boxed{y = e^{2(x^2\sin(x) + 2x\cos(x) + 2\cos(x) + \frac{\pi^2}{2} - 2)}}

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