What Is the Correct Derivative of sinhx/coshx?

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SUMMARY

The derivative of the function f(x) = sinh(x)/cosh(x) is correctly calculated using the quotient rule, yielding f'(x) = sech²(x). The discussion emphasizes the importance of applying the quotient rule accurately and recognizing hyperbolic identities, specifically that cosh²(x) - sinh²(x) = 1. Participants clarified that sech(x) is equivalent to 1/cosh(x), leading to the final simplified result of sech²(x) for the derivative.

PREREQUISITES
  • Understanding of hyperbolic functions, specifically sinh(x) and cosh(x).
  • Familiarity with the quotient rule for derivatives.
  • Knowledge of hyperbolic identities, particularly cosh²(x) - sinh²(x) = 1.
  • Basic algebraic manipulation skills for simplifying expressions.
NEXT STEPS
  • Study the quotient rule in detail, including examples and common pitfalls.
  • Learn about hyperbolic function identities and their applications in calculus.
  • Practice finding derivatives of various hyperbolic functions.
  • Explore the relationship between hyperbolic and trigonometric functions.
USEFUL FOR

Students studying calculus, particularly those focusing on derivatives of hyperbolic functions, as well as educators seeking to clarify concepts related to the quotient rule and hyperbolic identities.

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derivative help!

Homework Statement


find f'(x) sinhx/coshx


Homework Equations


this is what i got but I am unsure if its wrong could anyone help me pleasee


The Attempt at a Solution


coshx(sinhx)-(coshx)coshx/coshx... is this right if not help please
 
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How are you getting that? Write down the quotient rule for the derivative of f(x)/g(x) and check the parts.
 


ok i took a look at the quotient rule and was completely wrong how does this look...

coshx(coshx)-sinhx(sinhx)/(coshx)^2..... (Coshx)^2-(Sinhx)^2/(Coshx)^2...the (coshx)^2 cancel out and you are left with -(sinhx)^2?
 


Still not right. Cosh(x)^2 does not simply cancel out and vanish. If I asked you what 5/5 was equivalent to would you say zero?

To get the correct answer use the identity cosh(x)^2 - sinh(x)^2 = 1 or the identity 1 - tanh(x)^2 = sech(x)^2
 


ooooooo the identity oo ok so its 1/(coshx)^2?
 


Can you simplify that further?
 


no i get zero if i do the quotient rule again...?
 


No, you don't need to apply the quotient rule again nor should you; moreover, the derivative of 1/cosh(x)^2 is not zero.

Maybe you haven't been taught this but sech(x) = 1/cosh(x). Now simplify it.
 


oooo yessss i found it in my notebook in the hyperbolic functions would it be sech^2x??
 
  • #10


Yes, d(tanh(x))/dx = sech(x)^2.
 
  • #11


ldbaseball16 said:

Homework Statement


find f'(x) sinhx/coshx
You've come to this Web site, so I suppose that means you would like some help. You've taken the first step, which is to show us what you're tried to do. Good.

One thing you can do to help your cause is to provide meaningful information.
"find f'(x) sinhx/coshx"
Given just this information, I wouldn't know what to do. You're asking us to find the derivative of some function, but you haven't explicitly told us what the function is. Of course, we might infer that f(x) = sinhx/coshx, and you want to find f'(x).
ldbaseball16 said:

Homework Equations


this is what i got but I am unsure if its wrong could anyone help me pleasee


The Attempt at a Solution


coshx(sinhx)-(coshx)coshx/coshx... is this right if not help please

It's harder to write mathematical expressions on a single line than on paper, where you can write fractions more easily. When you have to write a complicated expression with fractions on a single line, make sure that you put a pair of parentheses around the entire numerator and another around the entire denominator. For example, if I write 3 + 1/4, most anyone would interpret this as 3 1/4, not as 4/4 = 1.
 

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