Part 1) To find the measure of ∠A in ∆ABC, use
we know that
In the triangle ABC
Applying the law of sines

in this problem we have

therefore
the answer Part 1) is
Law of Sines
Part 2) To find the length of side HI in ∆HIG, use
we know that
In the triangle HIG
Applying the law of cosines

In this problem we have
g=HI
G=angle Beta
substitute


therefore
the answer Part 2) is
Law of Cosines