So here is my question, I understand how to derive the cosine rule from, both triangles acute and obtuse. My problem is the 3 formula you get from this equation.(adsbygoogle = window.adsbygoogle || []).push({});

When I derive from a triangle I get the formula: [itex]c^2=a^2+b^2-2abcos∅[/itex]

so how do you derive the other two formula, I read that the letter are interchangeable so you can place them where every you like on the triangle. If that is the case, why do we show the other two formula? I presume people reading this post know of the other two formula I am referring to if not here they are: [itex]a^2=c^2+b^2-2cbcos∅[/itex]

[itex]b^2=a^2+c^2-2accos∅[/itex].

This has been on my mind for a while, I would appreciate if someone could clarify my confusion. Big thanks in advance.

**Physics Forums - The Fusion of Science and Community**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Cosine rule confusion

Loading...

Similar Threads - Cosine rule confusion | Date |
---|---|

B Sine/Cosine behaving like a linear function | Jan 11, 2018 |

I Demo of cosine direction with curvilinear coordinates | Dec 6, 2017 |

Cosines rule and sine rule | Oct 7, 2012 |

Cosine rule problems | Nov 4, 2011 |

Cosine Rule , what good is it ? | Oct 16, 2006 |

**Physics Forums - The Fusion of Science and Community**