Question

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Answer 1

Sorry, I have no idea. I haven't taken trigonometry yet >.<

Answer 2

You know the one angle. You know the two side lengths coming from that angle. Thus the end points of the the third side are defined.

A triangle has three angles and three sides. As long as they give you three things, you can solve for the other three. They could give you

SSA (side, side, angle)
SSS
SAA
AAA

Under those conditions, the triangle will always have just one solution.

Answer 3

Anytime.