Identidades de Suma a Producto

$$sen \: \alpha + sen \: \beta = 2 \: sen \: (\frac{\alpha + \beta}{2}) cos \: (\frac{\alpha - \beta}{2})$$

$$sen \: \alpha - sen \: \beta = 2 \: cos \: (\frac{\alpha + \beta}{2}) sen \: (\frac{\alpha - \beta}{2})$$

$$cos \: \alpha + cos \: \beta = 2 \: cos \: (\frac{\alpha + \beta}{2}) cos \: (\frac{\alpha - \beta}{2})$$

$$cos \: \alpha - cos \: \beta = -2 \: sen \: (\frac{\alpha + \beta}{2}) sen \: (\frac{\alpha - \beta}{2})$$