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Ch. 7 - Transcendental Functions
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Non è quello che usi tu?Cambia libro di testo
Capitolo 7, Problema 7.7.19

In Exercises 13–24, find the derivative of y with respect to the appropriate variable.
19. y = (sech θ)(1-ln(sech θ))

Guida verificata passo dopo passo
1
Identify the function to differentiate: \(y = (\text{sech} \ \theta)(1 - \ln(\text{sech} \ \theta))\). Notice this is a product of two functions of \(\theta\).
Apply the product rule for derivatives: If \(y = u(\theta) \cdot v(\theta)\), then \(\frac{dy}{d\theta} = u'(\theta) v(\theta) + u(\theta) v'(\theta)\), where \(u(\theta) = \text{sech} \ \theta\) and \(v(\theta) = 1 - \ln(\text{sech} \ \theta)\).
Find the derivative of \(u(\theta) = \text{sech} \ \theta\). Recall that \(\frac{d}{d\theta} \text{sech} \ \theta = -\text{sech} \ \theta \tanh \ \theta\).
Find the derivative of \(v(\theta) = 1 - \ln(\text{sech} \ \theta)\). Use the chain rule: \(\frac{d}{d\theta} \ln(\text{sech} \ \theta) = \frac{1}{\text{sech} \ \theta} \cdot \frac{d}{d\theta} \text{sech} \ \theta\). Substitute the derivative of \(\text{sech} \ \theta\) from the previous step.
Combine all parts using the product rule formula: \(\frac{dy}{d\theta} = u'(\theta) v(\theta) + u(\theta) v'(\theta)\), then simplify the expression as much as possible.

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Derivative of Hyperbolic Functions

Hyperbolic functions like sech(θ) have specific derivatives; for example, the derivative of sech(θ) is -sech(θ) tanh(θ). Understanding these derivatives is essential to differentiate expressions involving hyperbolic functions correctly.
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