# Quick calculus question

**URL:** <https://boards.straightdope.com/t/quick-calculus-question/157765>\
**Category:** Factual Questions\
**Created:** [February 27, 2003, 12:41am UTC](https://boards.straightdope.com/t/quick-calculus-question/157765 "2003-02-27T00:41:15Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Alietta](https://avatars.discourse-cdn.com/v4/letter/a/ecb155/32.png) [@Alietta](https://boards.straightdope.com/u/Alietta)\
**Post date:** [February 27, 2003, 12:41am UTC](https://boards.straightdope.com/t/quick-calculus-question/157765/1 "2003-02-27T00:41:15Z")

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How do I differentiate f(x)= yx?

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**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\
**Post date:** [February 27, 2003, 12:44am UTC](https://boards.straightdope.com/t/quick-calculus-question/157765/2 "2003-02-27T00:44:23Z")

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Properly, you’d have to use the product rule. df/dx = y + xdy/dx. If y is independent of x, then dy/dx is 0, and df/dx = y.

The concept you’re looking for is a “partial derivative”. If you google on that, you’ll find lots of info.

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<div class="post-metadata">

**Author:** ![Alietta](https://avatars.discourse-cdn.com/v4/letter/a/ecb155/32.png) [@Alietta](https://boards.straightdope.com/u/Alietta)\
**Post date:** [February 27, 2003, 1:20am UTC](https://boards.straightdope.com/t/quick-calculus-question/157765/3 "2003-02-27T01:20:27Z")

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How would I integrate it?

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<div class="post-metadata">

**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\
**Post date:** [February 27, 2003, 2:12am UTC](https://boards.straightdope.com/t/quick-calculus-question/157765/4 "2003-02-27T02:12:34Z")

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Again, if y is independent of x, the integral is yx[sup]2[/sup]/2 + c. If not, you have to integrate by parts.