The airplane Li’s family will be flying on can seat up to 149 passengers. If 96 passengers are currently on the plane, which inequality can be used to determine how many more people can board? 96 + x Less-than-or-equal-to 149
96 + x Greater-than-or-equal-to 149
96 + x > 149
96 + x < 149

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) = .