4. Which table shows y as a function of x?
F.
H.
-13
-13
-13
-13
х
1
3
7
12
у
-2
0
5
7
у
4
4
4
4
G.
J.
X
-6
-1
-1
10
x
-9
-2
0
0
y
3
-1
5
-9
у
-7
-5
0
6

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) = .