Mathc initiation/a0088
Calculons la dérivée :
y = coth(x)
y = cosh(x)/sinh(x)
y'= ( cosh(x)/sinh(x) )'
y'= sinh(x)sinh(x) - cosh(x)cosh(x)
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sinh(x)**2
y'= -[cosh(x)**2-sinh(x)**2]
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sinh(x)**2
y'= -1
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sinh(x)**2
y'= -csch(x)**2