দেওয়া আছে, $p = \tan \alpha - \tan \beta = \frac{\sin(\alpha-\beta)}{\cos \alpha \cos \beta}$ এবং $q = \cot \beta - \cot \alpha = \frac{\sin(\alpha-\beta)}{\sin \alpha \sin \beta}$। $$ \begin{aligned} \frac{1}{p} &= \frac{\cos \alpha \cos \beta}{\sin(\alpha-\beta)} \\ \frac{1}{q} &= \frac{\sin \alpha \sin \beta}{\sin(\alpha-\beta)} \\ \frac{1}{p} + \frac{1}{q} &= \frac{\cos \alpha \cos \beta + \sin \alpha \sin \beta}{\sin(\alpha-\beta)} \\ &= \frac{\cos(\alpha-\beta)}{\sin(\alpha-\beta)} = \cot(\alpha-\beta) \end{aligned} $$ যেহেতু $\alpha-\beta = \theta$, তাই $\cot \theta = \frac{1}{p} + \frac{1}{q}$।