on Tuesday at low tide the water was 17 ft below sea level. Then it rained for three days and the water level rose 20 feet. On Saturday it the water level dropped 5 ft and by Sunday it dropped another 3 feet. what was the water level by the end of the day on Sunday?

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Period is the time it takes for one “cycle” to complete. in the parent sine function, period is 2*pi since sin(0) = 0, sin(pi/2) = 1, sin(pi) = 0, sin(3pi/2) = -1, and sin(2pi) = 0. at that point, the sequence repeats itself. i’m not sure if your graph is similar to the sine function since you didn’t provide a picture, but you can find the period by looking at a graph.