The rotating light on a lighthouse is 400 feet from a cliff. it completes one rotation every 10 seconds. the equation representing the distance, d, in feet that the center of the circle of light is from the lighthouse is d(t) = 400sec (πt/5). what is the period of d(t)? (enter only the number.)

The period is [2(pi)] / |b| 

so, it would be 2pi / pi/5 = 10 

for the second part, just plug in 10 where the "t" is. 

400sec(10pi/5) or 400sec(2pi) 

Sec = 1 / cos 

SO, you get 400*(1/cos(2pi)) = 400* 1/1 = 400. since cos(2pi) = 1 
so you get 400 as your answer 

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