Show that point (pi/3,1/2) is on the curve of y=cosx

Acar started driving from city a to city b, distance between which is 620 miles, at a rate of 60 mph. two hours later a truck left city b and started moving towards city a at a rate of 40 mph. how many hours after the truck's departure will the two meet?

You eat $0.85 for every cup of hot chocolate you sell. how many cups do you need to sell to earn $55.25

What is the answer to question 11? will give extra points! include a explanation (reasonable) for you : )