Question

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Answer 1

well we don't know the measurements, so we can't find the missing sign. however, the law of cosine is:
\[a^2=b^2+c^2-2bc(cosA)\]
the law of cosines is used when you have two side lengths and one angle in the form of a V:
and you're trying to findthe side length of the opposite angle's side. (a=?)
law of sine is:
\[\frac{ sinA }{ a }=\frac{ sinB }{ b }=\frac{ sinC }{ c }\]
and this works when you either have:
2 side length and 1 angle and you're trying to find the other angle
OR
1 side length and 2 angles and you're trying to find the other side length.