/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 58 Use the identity $$\cot ^{-1} ... [FREE SOLUTION] | 91Ó°ÊÓ

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Use the identity $$\cot ^{-1} u=\frac{\pi}{2}-\tan ^{-1} u$$ to derive the formula for the derivative of \(\cot ^{-1} u\) in Table 3.1 from the formula for the derivative of \(\tan ^{-1} u\).

Short Answer

Expert verified
The derivative of \(\cot^{-1} u\) is \(-\frac{1}{1+u^2}\).

Step by step solution

01

Understand the Given Identity

We have the identity \(\cot ^{-1} u=\frac{\pi}{2}-\tan ^{-1} u\). This means that the inverse cotangent can be expressed as a difference between \(\frac{\pi}{2}\) and the inverse tangent of \(u\). We will use this identity to find the derivative of \(\cot^{-1} u\) using the derivative of \(\tan^{-1} u\).
02

Recall the Derivative of Inverse Tangent

The formula for the derivative of \(\tan^{-1} u\) is \(\frac{d}{du}(\tan^{-1} u) = \frac{1}{1+u^2}\). We will use this derivative in the next steps to find the derivative of \(\cot^{-1} u\).
03

Differentiate the Identity

Differentiate both sides of the identity \(\cot^{-1} u = \frac{\pi}{2} - \tan^{-1} u\) with respect to \(u\). The derivative of \(\frac{\pi}{2}\) is zero, and using the chain rule, we get:\[\frac{d}{du}(\cot^{-1} u) = 0 - \frac{d}{du}(\tan^{-1} u) = - \frac{1}{1+u^2}\]
04

Conclusion

Therefore, the derivative of \(\cot^{-1} u\) with respect to \(u\) is \(-\frac{1}{1+u^2}\). We found this by using the given identity and the known derivative of the inverse tangent function.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Understanding Cotangent
Cotangent is a trigonometric function that is the reciprocal of the tangent function. If you know tangent, you can imagine cotangent as turning your triangle upside down. It is often abbreviated as "cot". For an angle \(\theta\) in a right triangle, it can be expressed as:
  • \(\cot(\theta) = \frac{1}{\tan(\theta)}\)
  • It is also \(\cot(\theta) = \frac{\text{adjacent}}{\text{opposite}}\)
Cotangent is essential in various mathematical applications, including calculus and trigonometry itself. It helps solve problems where the focus is on angles and their respective ratios. To understand cotangent in the context of this exercise, we see its role in finding derivatives and linking to inverse functions. Remember, understanding cotangent's basic identity is a step towards mastering inverse trigonometric identities.
Tangent Function Explained
Tangent is a crucial trigonometric function that compares the length of the opposite side to the adjacent side in a right triangle.Expressed as:
  • \(\tan(\theta) = \frac{\text{opposite}}{\text{adjacent}}\)
  • It can also be seen as \(\tan(\theta) = \frac{1}{\cot(\theta)}\)
In calculus, its importance grows as it appears in derivative and integral calculations. Tangent functions oscillate and have asymptotes, which make them unique to deal with.In the context of inverse functions, the tangent function is pivotal. In this exercise, we recall the derivative of the inverse tangent, \(\tan^{-1} u\), as it directly helps in deriving the derivative of \(\cot^{-1} u\). The tangent, thus, acts as a foundation to understand its reciprocal and inverse identities better.
The Magic of Derivatives
Derivatives in calculus are a powerful tool. They measure how a function changes as its input changes. Some basics include:
  • The derivative of a constant is zero.
  • The derivative of a sum is the sum of the derivatives.
When dealing with trigonometric functions, derivatives help in understanding the rate of change of angles and trajectories. For instance, the derivative of \(\tan^{-1} u\) is \(\frac{1}{1+u^2}\). While using the identity given in this exercise, we apply the derivative of \(\tan^{-1} u\) to find the derivative of \(\cot^{-1} u\). It shows how derivatives bridge functions, translating static identities into dynamic change patterns.
Exploring Inverse Functions
Inverse functions reverse operations of original functions. They swap the input-output roles.For trigonometric functions, they help in finding angle measures from given ratios. Understanding inverse functions requires understanding their original formats.For instance, with
  • \(\tan^{-1}(u)\), it gives angle \(\theta\) such that \(\tan(\theta) = u\).
  • \(\cot^{-1}(u)\) gives an angle \(\theta\) such that \(\cot(\theta) = u\).
In this exercise, using the given identity, we find that inverse functions like \(\tan^{-1}(u)\) and \(\cot^{-1}(u)\) are interconnected. Their identity involves trigonometric angles, helping find derivative expressions using simple transformations. Inverse functions play a crucial role in understanding the relationships in trigonometry.

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Most popular questions from this chapter

You will explore some functions and their inverses together with their derivatives and tangent line approximations at specified points. Perform the following steps using your CAS: a. Plot the function \(y=f(x)\) together with its derivative over the given interval. Explain why you know that \(f\) is one-to-one over the interval. b. Solve the equation \(y=f(x)\) for \(x\) as a function of \(y,\) and name the resulting inverse function \(g\). c. Find an equation for the tangent line to \(f\) at the specified $$ \text { point }\left(x_{0}, f\left(x_{0}\right)\right) $$ d. Find an equation for the tangent line to \(g\) at the point \(\left(f\left(x_{0}\right), x_{0}\right)\) located symmetrically across the \(45^{\circ}\) line \(y=x\) (which is the graph of the identity function). Use Theorem 3 to find the slope of this tangent line. e. Plot the functions \(f\) and \(g\), the identity, the two tangent lines, and the line segment joining the points \(\left(x_{0}, f\left(x_{0}\right)\right)\) and \(\left(f\left(x_{0}\right), x_{0}\right) .\) Discuss the symmetries you see across the main diagonal (the line \(y=x\) ). $$y=e^{x}, \quad-3 \leq x \leq 5, \quad x_{0}=1$$

Measuring acceleration of gravity When the length \(L\) of a clock pendulum is held constant by controlling its temperature, the pendulum's period \(T\) depends on the acceleration of gravity \(g\). The period will therefore vary slightly as the clock is moved from place to place on Earth's surface, depending on the change in \(g\). By keeping track of \(\Delta T\), we can estimate the variation in \(g\) from the equation \(T=2 \pi(L / g)^{1 / 2}\) that relates \(T, g,\) and \(L\) a. With \(L\) held constant and \(g\) as the independent variable, calculate \(d T\) and use it to answer parts (b) and (c). b. If \(g\) increases, will \(T\) increase or decrease? Will a pendulum clock speed up or slow down? Explain. c. A clock with a \(100-\mathrm{cm}\) pendulum is moved from a location where \(g=980 \mathrm{cm} / \mathrm{sec}^{2}\) to a new location. This increases the period by \(d T=0.001\) sec. Find \(d g\) and estimate the value of g at the new location.

Find the domain and range of each composite function. Then graph the composition of the two functions on separate screens. Do the graphs make sense in each case? Give reasons for your answers. Comment on any differences you see. a. \(y=\sin ^{-1}(\sin x)\) b. \(y=\sin \left(\sin ^{-1} x\right)\)

Use a CAS to perform the following steps. a. Plot the equation with the implicit plotter of a CAS. Check to see that the given point \(P\) satisfies the equation. b. Using implicit differentiation, find a formula for the derivative \(d y / d x\) and evaluate it at the given point \(P\) c. Use the slope found in part (b) to find an equation for the tangent line to the curve at \(P .\) Then plot the implicit curve and tangent line together on a single graph. $$x y^{3}+\tan (x+y)=1, \quad P\left(\frac{\pi}{4}, 0\right)$$

Find the derivative of \(y\) with respect to the given independent variable. $$y=3^{\log _{2} t}$$

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