If x^2 +y^2 =25 and dy/dt = 6, find dx/dt when y = 4 When I did this, I got positive and negative three, but that can't be right. What is the right way to do this?
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The curve is the circle of radius 5, at y=4, which means x could be -3 or 3. Fully differentiate: 2x x' + 2y y' = 0 x x' + y y' = 0 x x' + 4*6 = 0 x' = 24/x so dx/dt is 8 or -8. Only one answer is expected here?
Originally Posted by bobsanchez If x^2 +y^2 =25 and dy/dt = 6, find dx/dt when y = 4 When I did this, I got positive and negative three, but that can't be right. What is the right way to do this? is a circle centred at the origin (0,0) with radius=5. Hence, when y=4, The radius is unchanging.. Solve this at (3,4) and (-3,4).
No, two answers were expected.
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