Question

Help me on problem 21

Answer 1

See below.


First make a diagram of the situation as shown: We are looking to find the distance RT.

The Cosine Rule states, for a triangle ABC.

a2=b2+c2−2bc⋅cos(C)

Making C=S=120∘

We have:

(RT)2=(ST)2+(RS)2−2(ST)(RS)⋅cos(S)

(RT)2=2002+1502−2(200)(150)⋅cos(120∘)

So the first one is the correct solution.