Differential equation of the family of ellipses having foci on y-axis ...
The differential equation of the family of ellipses having foci on the y-axis and center at the origin can be found as follows:
Let's consider an ellipse with foci (0, c) and (0, -c), where c is a positive constant. The distance between the foci is 2c.
The general equation of an ellipse centered at the origin is given by:
x^2/a^2 + y^2/b^2 = 1,
where a and b are positive constants representing the semi-major and semi-minor axes, respectively.
Since the foci lie on the y-axis, the equation of the ellipse becomes:
x^2/a^2 + (y - c)^2/b^2 = 1.
We know that the distance between the foci is 2c, so we have:
2c = 2b^2/a.
Simplifying this equation, we get:
b^2 = ac.
Now, differentiating both sides of the equation with respect to x, we have:
2b(b') = a'c + ac',
where b' and a' represent the derivatives of b and a with respect to x, respectively.
Since the derivatives of a and b are unknown, we cannot solve for the differential equation in terms of x and y directly. However, we can eliminate a' and b' by using the relationship b^2 = ac, which gives:
2b(b') = 2b(c'/b) + ac'.
Simplifying this equation, we find:
b' = c'/b + ac'/(2b^2).
Rearranging terms, we get:
b'(2b^2) = c' + ac'.
Substituting b^2 = ac, we obtain:
b'(2b^2) = c' + b^2c'.
Finally, dividing both sides by 2b^2, we get the differential equation:
b' = (c' + b^2c')/(2b^2).
Therefore, the differential equation of the family of ellipses having foci on the y-axis and center at the origin is:
b' = (c' + b^2c')/(2b^2).
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