## sweett2639 2 years ago A point moves around the circle x^2 +y^2 = 9. when the point is at (square root of -3, square root of 6) its x coordinate is increasing at the rate of 20 units per second. How fast is the y coordinate changing at that instant?

1. imron07

Find the rate of increase of the function first: $x^2+y^2=9\\\frac{dx^2}{dt}+\frac{dy^2}{dt}=0\\2xx'+2yy'=0\\y'=\frac{x}{y}x'$

2. imron07

Then plug all knowns in ;)

3. sweett2639

im still confused :/

4. Chlorophyll

@sweett2639 Firstly do you know how to take derivative?

5. baldymcgee6

|dw:1351482694919:dw|First label all our variables and rates.