Hey there again, I need help with this other question:

A cyclist rides one lap of a cicular track at a constant speed so that her distance, d metres, from her starting point at any time, t sec, after starting is:
d=50-50cos[(PI times t)/30]

Find:
a) the time taken to complete one lap
b) the radius of the track
c) the maximum distance from the start
d) the length of the track

Thanks and please give me tips on how to solve d or/and the others if you want.

Is it Cost or Cos?

My bad because

a. d=50-50cos[(PI times t)/30]

When one lap is completed, d = 0

50cos[(PI times t)/30] = 50

cos[(PI times t)/30] = 1

[(PI times t)/30] = 0, pi, 2 pi,. (Radians)

t/30 = 0, 1, 2,.

t = 0, 30, 60,.

Time for 1 lap = 30 seconds

c. Let r be radius.

What is the maximum distance from start?

It is = 2r (Diameter).

What is maximum value of d = 50-50cos[(PI times t)/30] ?

Minimum value of Cos is 0.

Hence maximum value of d is 50

b. 2 r = 50

r = 25

d. Length of track = circumference = 2(pi)r