Associated Topics || Dr. Math Home || Search Dr. Math

### Implicit Differentiation

```
Date: 11/4/96 at 12:29:14
From: Scott Thompson
Subject: Implicit Differentiation

Here's my question:

Find the slope of the tangent at the point (3,4) on the circle
x^2 + y^2 = 25.

My answer: I guess we would need to put it in the y = mx + b form.

Thanks for any help,
Scott
```

```
Date: 11/05/96
From: Doctor Pete
Subject: Re: Implicit Differentiation

To find the slope of the tangent at the point (3,4) on the circle
x^2 + y^2 = 25 you need to use implicit differentiation.  You cannot
put a circle into the form of a line.  In particular, you want to find
dy/dx:

d/dx[x^2 + y^2 = 25] ==> 2x + 2y dy/dx = 0.

Can you complete the solution?

-Doctor Pete,  The Math Forum
Check out our web site!  http://mathforum.org/dr.math/

```
Associated Topics:
High School Calculus

Search the Dr. Math Library:

 Find items containing (put spaces between keywords):   Click only once for faster results: [ Choose "whole words" when searching for a word like age.] all keywords, in any order at least one, that exact phrase parts of words whole words

Submit your own question to Dr. Math
Math Forum Home || Math Library || Quick Reference || Math Forum Search

Ask Dr. MathTM
© 1994- The Math Forum at NCTM. All rights reserved.
http://mathforum.org/dr.math/