Akiko leaves the mall and drives directly west at a speed of 60 mph. At the same time, Kosuke leaves the mall and drives 40 degrees north of east at a speed of 45 mph. How far apart are they after 45 minutes? Round the answer to the nearest tenth of a mile.

A. 17.4 miles B. 28.9 miles C. 44.5 miles D. 74.1 miles

You know that Akiko is 45 miles from the origin ... Kosuke is (135/4) miles from the origin ... You can draw a figure to clearly see the situation.

you "know" that the angle between their routes is 140º

the side opposite (140º) is the distance between them ...

c^2 = (45) ^2 + (135/4) ^2 - 2 (45) (135/4) cos 140

c ≈ 74.1 mile

Hope this answers the question.