Answer:
∠ ABC ≈ 137.9°
Step-by-step explanation:
Using the Cosine rule in Δ ABC
cos B = [tex]\frac{a^2+c^2-b^2}{2ac}[/tex]
with a = 89, b = 144, c = 65
cos B = [tex]\frac{89^2+65^2-144^2}{2(89)(65)}[/tex] = [tex]\frac{7921+4225-20736}{11570}[/tex] = [tex]\frac{-8590}{11570}[/tex] , thus
B = [tex]cos^{-1}[/tex] ( - [tex]\frac{8590}{11570}[/tex] ) ≈ 137.9° ( to the nearest tenth )
