# Math Help - implicit functions

1. ## implicit functions

ok so I've got the implicit differentiation down, now i need help on how to find the tangent line...for example...

x^2 + y^2 - 5x + 7y = 13

dy/dx = (-2x+5)/(2y+7)

Under what condition on x is the tangent line to the curve horizontal?

Under what condition on y is the tangent line to the curve vertical?

mathaction

2. 1)If the tangent line is horizontal then it has no slope or a slope of 0. So in order to find out where the slope is zero, in this case, set -2x+5=0

2)If the tangent line is verical then we have divided by zero because there is an infinite slope. In this case, we need the denomiator to equal zero so find out what value of y makes it so.

3. Originally Posted by Jameson
1)If the tangent line is horizontal then it has no slope or a slope of 0. So in order to find out where the slope is zero, in this case, set -2x+5=0

2)If the tangent line is verical then we have divided by zero because there is an infinite slope. In this case, we need the denomiator to equal zero so find out what value of y makes it so.
yeah i figured this one out already...i took a second look, then felt stupid, but thanks anyway...