Answer:
3.40 km
Step-by-step explanation:
Given two sides and the angle between them, the Law of Cosines is useful for finding the remaining side of the triangle.
If we call the vertices of the triangle H, P, Y, then the Law of Cosines tells you ...
HY² = HP² +YP² -2HP·YP·cos(P)
HY² = 6² +7² -2·6·7·cos(29°) = 85 -84·cos(29°) ≈ 11.531944
HY ≈ √11.531944 ≈ 3.40 . . . . km
The length of the tunnel is about 3.40 km.
