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Answer:
B. The lengths of two of the triangle's sides and the measure of the angle between them
Step-by-step explanation:
The usual formulation of the law of cosines is something like this:
c² = a² +b² -2ab·cos(C)
where 'c' is the side opposite angle C, and 'a' and 'b' are the other two sides. That is, to use this formula directly, one needs two side lengths and the measure of the included angle.
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<em>Additional comment</em>
One can use the law of cosines to solve a triangle when any two sides and one angle are known. The use of the formula will give a quadratic in the unknown side length, if it is not the side opposite the known angle. As with the law of sines, if the angle is opposite the shorter of the two given sides, there may be two solutions for the length of the third side.
