Posted by Ken on Sunday, November 25, 2012 at 10:07pm.
An object is moving along a circle of radius 5 . When the object is at the point (−4,3) , the y value of its position is changing at the rate of 9 units per second. How fast is the x value of its position changing at that moment?

Math Calc  Steve, Monday, November 26, 2012 at 12:09am
x^2 + y^2 = 25
2x dx/dt + 2y dy/dt = 0
2(4) dx/dt + 2(3)(9) = 0
8 dx/dt + 54 = 0
dx/dt = 54/8 = 27/4 = 6.75
makes sense; the particle is moving up to the right.