Answer:
90°
Step-by-step explanation:
note that
simplifies to 
There are 360° in one turn of the circle , then
× 360° = 360° ÷ 4 = 90°
During the 9 mile hike he spends 2 periods of half hour swimming = 1 hour.
actual hiking time = 3*3 = 9 hours
So total time = 9+1 = 10 hours