An integrating factor for (cos y sin 2x)dx + (cos2 y - cos2 x)dy = 0 i...
Given equation:
(cos y sin 2x)dx + (cos2 y - cos2 x)dy = 0
Step 1: Identify the form of the equation
The given equation is not in the standard form for exact differential equations, which is M(x, y)dx + N(x, y)dy = 0. To transform it into this form, we need to multiply an integrating factor.
Step 2: Find the integrating factor
To find the integrating factor, we need to check if the equation satisfies the exactness condition, which states that ∂M/∂y = ∂N/∂x.
In this case,
∂(cos y sin 2x)/∂y = cos 2x
∂(cos2 y - cos2 x)/∂x = 2cos2 x
Since cos 2x and 2cos2 x are not equal, the equation is not exact. Therefore, we need to find an integrating factor.
Step 3: Find the integrating factor
The integrating factor (IF) for a first-order linear differential equation of the form M(x, y)dx + N(x, y)dy = 0 can be found using the formula:
IF = e^(∫(∂M/∂y - ∂N/∂x)/N dx)
In this case, we have:
∂M/∂y - ∂N/∂x = cos 2x - 2cos2 x
IF = e^(∫(cos 2x - 2cos2 x)/(cos2 y - cos2 x) dx)
Step 4: Simplify the integral
To simplify the integral, we can use the trigonometric identity cos 2x = 2cos^2 x - 1.
IF = e^(∫(2cos^2 x - 2cos2 x)/(cos2 y - cos2 x) dx)
IF = e^(∫(2cos^2 x - 2(2cos^2 x - 1))/(cos2 y - cos2 x) dx)
IF = e^(∫(2 - 4cos^2 x)/(cos2 y - cos2 x) dx)
IF = e^(∫(2(1 - 2cos^2 x))/(cos2 y - cos2 x) dx)
Step 5: Simplify the integral further
We can simplify the integral by using the trigonometric identity sin^2 x = 1 - cos^2 x.
IF = e^(∫(2(1 - 2cos^2 x))/(cos2 y - cos2 x) dx)
IF = e^(∫(2(1 - 2(1 - sin^2 x)))/(cos2 y - cos2 x) dx)
IF = e^(∫(2(1 - 2 + 2sin^2 x))/(cos2 y - cos2 x) dx)
IF = e^(∫(4sin^2 x - 2)/(cos2 y - cos2 x) dx)
Step 6: Evaluate the integral
Let's integrate the expression inside the exponential:
∫(4
An integrating factor for (cos y sin 2x)dx + (cos2 y - cos2 x)dy = 0 i...