Ley de Tangentes

$$\frac{a-b}{a+b}=\frac{tan[\frac{1}{2}(\alpha - \beta)]}{tan[\frac{1}{2}(\alpha + \beta)]}$$

$$\frac{b-c}{b+c}=\frac{tan[\frac{1}{2}(\beta - \gamma)]}{tan[\frac{1}{2}(\beta + \gamma)]}$$

$$\frac{a-c}{a+c}=\frac{tan[\frac{1}{2}(\alpha - \gamma)]}{tan[\frac{1}{2}(\alpha + \gamma)]}$$