A directed line segment angles α, β, γ with the coordinate axes. The value of ∑ cos 2α is always equal to :
Answer & explanation
Correct answer: option 1
$\sum \cos 2 \alpha=\sum\left(2 \cos ^2 \alpha-1\right)$
$=2 \sum \ell^2-3$
$=-1$
A directed line segment angles α, β, γ with the coordinate axes. The value of ∑ cos 2α is always equal to :
Correct answer: option 1
$\sum \cos 2 \alpha=\sum\left(2 \cos ^2 \alpha-1\right)$
$=2 \sum \ell^2-3$
$=-1$