Answer:
11.8
Step-by-step explanation:
You want side c of obtuse ∆ABC with a=10, b=3, C=120°.
Law of cosines
The given values can be used in the given law of cosines formula to find ...
c² = a² +b² -2ab·cos(C)
c² = 10² +3² -2(10)(3)·cos(120°) = 100 +9 -60(-0.5) = 139
c = √139 ≈ 11.8
The length of side c is about 11.8 units.
