In february, alec had 1,513 visitors to his website. in march, he had 1,381 visitors to his website. what is the percentage decrease of the number of visitors to alec's website from february to march? if necessary, round to the nearest tenth of a percent. 91.3% 10.5% 8.7% 9.6%

Subtract old value (1513) from new value (1381): 1381 - 1513 = -132
The negative tells you it is a percentage decrease...now ignore it.
Divide the amount of decrease (132) by the old value (1513): 
Multiply this number by 100: 0.087(100) = 8.7%

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.