Question

(cosine alpha+ cosine beta +cosine gamma)²​​=?

Answer 1

Dear Student,

$$\begin{gathered} {\left(\mathrm{cos\alpha }+\mathrm{cos\beta }+\mathrm{cos\gamma }\right)}^2 \\ ={\cos }^2\mathrm{\alpha }+{\cos }^2\mathrm{\beta }+{\cos }^2\mathrm{\gamma }+2\mathrm{cos\alpha cos\beta }+2\mathrm{cos\beta cos\gamma }+2\mathrm{cos\gamma cos\alpha } \end{gathered}$$

Regards