Question

ayuden a resolverlo

Answer 1

${r}^{2} = {a}^{2} + {b}^{2} + 2ab \cos( \alpha )$
$(2 \sqrt{19}) {}^{2} = {6}^{2} + {4}^{2} + 2(6)(4) \cos( \alpha )$
$\cos( \alpha ) = \frac{1}{2}$
$\alpha = 60$