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100台南二中

計算二

\(\displaystyle \frac{A}{2}+\frac{B}{2}+\frac{C}{2}=\frac{\pi}{2} \)

\(\displaystyle tan \frac{A}{2} tan \frac{B}{2} + tan \frac{A}{2} tan \frac{C}{2}+ tan \frac{B}{2} tan \frac{C}{2}=1 \)

\(\displaystyle tan \frac{A}{2} tan \frac{B}{2} + tan \frac{B}{2} tan \frac{C}{2}=\frac{2}{3}=2 tan \frac{A}{2} tan \frac{C}{2} \)

\(\displaystyle cot \frac{C}{2}+cot \frac{A}{2}=2 cot \frac{B}{2} \)

\(\displaystyle \frac{s-c}{r}+\frac{s-a}{r}=2 \frac{s-b}{r} \)

\(\displaystyle a+c=2b \)
名豈文章著官應老病休飄飄何所似Essential isolated singularity

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引用:
原帖由 waitpub 於 2011-5-11 07:05 PM 發表
請問這一步驟是怎麼來的?
\(\displaystyle cot \frac{C}{2}+cot \frac{A}{2}=2 cot \frac{B}{2} \)
就上一式同乘以
\(\displaystyle cot \frac{A}{2} cot \frac{B}{2} cot \frac{C}{2} \)
名豈文章著官應老病休飄飄何所似Essential isolated singularity

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