Suzie made a mistake in the following problem.

the mistake was made in line only input the number of the first incorrect line.

line 1

7(6) ÷ 5 + 42

line 2

7(6) ÷ 5 + 16

line 3

42 ÷ 5 + 16

line 4

42 ÷ 21

line 5

2

numerical answers expected!

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) = .