Answer: m∡B°=38,2°.
Step-by-step explanation:
a=3, b=5, c=7 ∡B°=?
[tex]b^2=a^2+c^2-2*a*ccosB^0\\2*a*c*cosB^0=a^2+c^2-b^2\\cosB^0=\frac{a^2+c^2-b^2}{2*a*c} \\cosB^0=\frac{3^2+7^2-5^2}{2*3*7} \\cosB^0=\frac{9+49-25}{2*3*7} \\cosB^0=\frac{33}{42} \\cosB^0=\frac{11}{14}\\[/tex]
m∡B°=arccos[tex](\frac{11}{14})[/tex]
m∡B°≈38,2°.
Good luck!
