need help fast

Find b!

Hello Guest!

 \(b^2=a^2+c^2-2ac\cdot cos 115^{\circ}\)

\(b^2=(28^2+18^2-2\cdot 28\cdot 18\cdot cos \ 115^{\circ})m^2\\ b^2=1534m^2\)

\(b=39.166m\)

  !