Find the solution of the differential equation that satisfies the given initial condition. y' tan x = 3a + y, y(π/3) = 3a, 0 < x < π/2, where a is a constant.

Respuesta :

Answer:

[tex]y(x)=4a\sqrt{3}* sin(x)-3a[/tex]

Step-by-step explanation:

We have a separable equation, first let's rewrite the equation as:

[tex]\frac{dy(x)}{dx} =\frac{3a+y}{tan(x)}[/tex]

But:

[tex]\frac{1}{tan(x)} =cot(x)[/tex]

So:

[tex]\frac{dy(x)}{dx} =cot(x)*(3a+y)[/tex]

Multiplying both sides by dx and dividing both sides by 3a+y:

[tex]\frac{dy}{3a+y} =cot(x)dx[/tex]

Integrating both sides:

[tex]\int\ \frac{dy}{3a+y} =\int\cot(x) \, dx[/tex]

Evaluating the integrals:

[tex]log(3a+y)=log(sin(x))+C_1[/tex]

Where C1 is an arbitrary constant.

Solving for y:

[tex]y(x)=-3a+e^{C_1} sin(x)[/tex]

[tex]e^{C_1} =constant[/tex]

So:

[tex]y(x)=C_1*sin(x)-3a[/tex]

Finally, let's evaluate the initial condition in order to find C1:

[tex]y(\frac{\pi}{3} )=3a=C_1*sin(\frac{\pi}{3})-3a\\ 3a=C_1*\frac{\sqrt{3} }{2} -3a[/tex]

Solving for C1:

[tex]C_1=4a\sqrt{3}[/tex]

Therefore:

[tex]y(x)=4a\sqrt{3}* sin(x)-3a[/tex]

The solution of the differential equation that satisfies the given initial condition is [tex]y = a\cdot (0.817\cdot 10^{\sin x}-3)[/tex].

Solution of a differential equation by variable separation

In this question we must separate variables on each side of the formula:

[tex]\frac{dy}{dx} \cdot \tan x = 3\cdot a + y[/tex]    

[tex]\int {\frac{dx}{\tan x} } = \int {\frac{dy}{3\cdot a+y} }[/tex]

[tex]\log (\sin x) + C = \log(3\cdot a + y)[/tex]

[tex]C\cdot 10^{\sin x} = 3\cdot a + y[/tex]

[tex]C = \frac{3\cdot a + y}{10^{\sin x}}[/tex] (1)

Where [tex]C[/tex] is the integration constant. If we know that [tex]y\left(\frac{\pi}{3} \right) = 3\cdot a[/tex], then the integration constant is:

[tex]C = \frac{6\cdot a}{10^{\frac{\sqrt{3}}{2} }}[/tex]

[tex]C \approx 0.817\cdot a[/tex] (2)

By (2) in (1):

[tex]0.817\cdot a \cdot 10^{\sin x} = 3\cdot a + y[/tex]

[tex]y = a\cdot (0.817\cdot 10^{\sin x}-3)[/tex]   (3)

The solution of the differential equation that satisfies the given initial condition is [tex]y = a\cdot (0.817\cdot 10^{\sin x}-3)[/tex]. [tex]\blacksquare[/tex]

To learn more on differential equations, we kindly invite to check this verified question: https://brainly.com/question/25731911