Question

Se considera triunghiul ABC: AB=4, AC=radical din7, BC=radical din3. Aflati masura unghiuluiB.

Answer 1

$AC^2=AB^2+BC^2-2*AB*BC*cosB \\ 7=16+3-2*4* \sqrt{3}*cosB \\ 7-16-3=-8 \sqrt{3}cosB \\ -12=-8 \sqrt{3}cosB \\ cosB= \frac{12}{8 \sqrt{3} } = \frac{3 \sqrt{3} }{6}= \frac{ \sqrt{3} }{2} \\ m(\ \textless \ B)=30$