Ment G
L
H Н
K
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In the figureheadabove, FL = HJ and ZL is congruent to ZH. Which
additional information would be sufficient to conclude that these two
triangles are congruent?
O A FG = (1/2)(FL)
O B. LJ is a right angle
O CLK = GH
D. FG = JK
DO

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) = .