Shalika bought a purse for $120. the tax rate is 9%. what is the total amount shalika paid?

9/100 = x/120
the cross multiply to get:

100x = 1080
divide I080 by 100 to get 10.8

Finally add a 10.8 to 120 ( the original amount) to get $130.80

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.