The amount of money americans spent on certain sporting equipment from 2004 to 2009
can be modeled by y = 8.5x + 350.5, where x represents the number of years after 2004 and
y represents the amount spent on equipment in millions of dollars. the actual data are graphed
here.

The mean of a set of data is -3.82 and its standard deviation is 2.31. find the z score for a value of 3.99.

Prove (a) cosh2(x) − sinh2(x) = 1 and (b) 1 − tanh 2(x) = sech 2(x). solution (a) cosh2(x) − sinh2(x) = ex + e−x 2 2 − 2 = e2x + 2 + e−2x 4 − = 4 = . (b) we start with the identity proved in part (a): cosh2(x) − sinh2(x) = 1. if we divide both sides by cosh2(x), we get 1 − sinh2(x) cosh2(x) = 1 or 1 − tanh 2(x) = .

Amir wants to proportionally increase the size of a photo to create a poster for his room. the size of the original photo is shown. complete the statement and then answer the question to represent ways that amir can increase the size of his photo.