N26112A GCE Further Pure Maths 6675 June 2007.indd - Edexcel

4. (a) Starting from the definitions of cosh and sinh in terms of exponentials, prove that
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cosh(A – B) = cosh A cosh B – sinh A sinh B .
(3)
(b) Hence, or otherwise, given that cosh(x – 1) = sinh x, show that
2
e + 1
tanh x = .
2
e + 2e−1
(4)
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*N26112A0824*