Cotangent of the sum of two angles
cosota
Trigonometry
The cotangent of the sum of two angles equals the product of the cotangents of the angles minus 1 divided by the sum of the cotangents of the two angles
\cot(\alpha+\beta) = \dfrac{\cot \alpha\cot \beta-1 }{\cot \alpha+\cot \beta}
or