请输入您要查询的字词:

 

单词 ProofOfCosinesLaw
释义

proof of cosines law


Let a, b, c be the sides of a triangle and α, β, γ its angles, respectively.  By the projection formula, one may write the equalities

{a=bcosγ+ccosβb=ccosα+acosγc=acosβ+bcosα.

Multiplying the equalities by a, -b and -c, respectively, they read

{a2=abcosγ+cacosβ-b2=-bccosα-abcosγ-c2=-cacosβ-bccosα.

Addition of these yields the sum equation

a2-b2-c2=-2bccosα,

i.e.

a2=b2+c2-2bccosα,

which is the cosines law.

随便看

 

数学辞典收录了18232条数学词条,基本涵盖了常用数学知识及数学英语单词词组的翻译及用法,是数学学习的有利工具。

 

Copyright © 2000-2023 Newdu.com.com All Rights Reserved
更新时间:2025/5/4 23:40:34