Question 1193267
Given the equation x^2+y^2=9 , express y explicitly and calculate the 
derivative.
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Not clear what you want to do.
But,
x^2+y^2=9
Differentiate ---> 2x*dx + 2y*dy = 0
x*dx = -y*dy
dy/dx = -x/y
The slope of the tangent to circle at any point is -x/y