Quod Erat Demonstrandum

2013/05/12

三角law

Filed under: Fun — johnmayhk @ 3:35 下午

除了 sine formula, cosine formula, tangent formula,還有

Cotangent formula

\frac{\cot\frac{A}{2}}{s-a}=\frac{\cot\frac{B}{2}}{s-b}=\frac{\cot\frac{C}{2}}{s-c}

(其中 s=\frac{a+b+c}{2}

Mollweide’s formula

\frac{a+b}{c}=\frac{\cos\frac{A-B}{2}}{\sin\frac{C}{2}}

\frac{a-b}{c}=\frac{\sin\frac{A-B}{2}}{\cos\frac{C}{2}}

頗有美感的式子吧。證明?同學試試了。

johnmayhk-sine-formula-t-shirt

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