Q.Find the differential equation of all the circles that pass through origin.

A.

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- March 9th 2008, 03:02 AMAltairSolution required
Q.Find the differential equation of all the circles that pass through origin.

A. - March 9th 2008, 03:36 AMmr fantastic
Well, I have a plan but you'll need to put in the details.

If the circle passes through the origin then .

Then the equation of the circle becomes

.... (1)

Differentiate (1) with respect to x:

.... (2)

Differentiate (2) with respect to x:

.... (3)

Clearly k needs to be eliminated from (3).

(1) and (2) can be solved simultaneously to get k and h in terms of x, y and y'. You want k. Substitute the result into (3). - March 10th 2008, 09:49 AMAltair
Need help with substitution. It gets too complicated at the end.

- March 10th 2008, 11:58 AMmr fantastic