Suppose a triangle has two sides of length 42 and 35, and that the angle between these two sides is 120. Which equation should you solve to find the
length of the third side of the triangle?

9514 1404 393

  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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Additional comment

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 c² =

step-by-step explanation: