posted by Anonymous .
The circle defined by the equation x^2 + y^2 = 18 has two points where the slope of its tangent line is m=1. Find those points.
LOL, sketch a graph !
Good idea. However, in an attempt to use your math, and also to apply to a possibly more general problem later, try implicit differentiation:
x^2 + y^2 = 18
2x + 2yy' = 0
y' = -x/y
So, if -x/y = 1 and x^2+y^2 = 18,
2x^2 = 18
x = ±3
Now, figuring y should not be too hard.