Answer:
Step-by-step explanation:
4.
2ab cos C=a²+b²-c²
2×31×14 cos C=31²+14²-40²
868 cos C=961+196-1600=-443
cos C=-443/868
C=cos^{-1}(-443/868)≈120.688≈120.69°
5.
by sine formula
m∠B=180-(62+55)=180-117=63°
[tex]\frac{AC}{sin~B} =\frac{AB}{sin~C} \\\frac{240}{sin 63} =\frac{AB}{sin~55} \\AB=\frac{sin~55}{sin~63} \times 240 \approx 220.645 \approx 220.65 ~ft[/tex]
