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Answer:
c = √(42² +35² -2·42·35·cos(120°))
Step-by-step explanation:
The third side can be found using the Law of Cosines. It will tell you ...
c² = a² +b² -2ab·cos(C)
where C is the angle opposite the third side (c). For the given side lengths, then the third side can be found from ...
c = √(42² +35² -2·42·35·cos(120°))
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<em>Additional comment</em>
You have not provided answer choices to this "which ..." problem. So the above equation may be different from any on your list. We expect your answer choices may leave the equation in the form <em>c² = ...</em>.
