Answer:
90. 04987916
Explanation:
Let HI be a
and GH be c
and GI be b
and <GHI be B
Using the law of Cosines,
b^2= -2ac cos (B) + c^2 + a^2
= -2(42)(60) cos (123)+60^2+42^2
= -5040 cos (123) +3600+1764
= -5040(-0. 544639035) +5364
= 2744. 980736+5364
b^2= 8108. 980736
b= Sqrt ( 8108. 980736)
b= 90. 04987916