# defining an implicit function

**URL:** <https://community.wolfram.com/t/defining-an-implicit-function/1064>\
**Category:** Questions\
**Tags:** physics\
**Created:** [December 6, 2013, 9:55pm UTC](https://community.wolfram.com/t/defining-an-implicit-function/1064 "2013-12-06T21:55:53Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![clejaniuval](https://avatars.discourse-cdn.com/v4/letter/c/dbc845/32.png) [@clejaniuval](https://community.wolfram.com/u/clejaniuval)\
**Post date:** [December 6, 2013, 9:55pm UTC](https://community.wolfram.com/t/defining-an-implicit-function/1064/1 "2013-12-06T21:55:53Z")

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I’d like to do some GR calculations with the Kruskal-Szekeres coordinates and the Schwartzchild metric (or other metrics). I have the RGTC package, but I don’t know how to define the metric with r, which is an implicit function of u and v (r/2M-1) Exp[r/2M]=u^2-v^2. Any way to define implicit functions in Mathematica?