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Ch. 3 - Derivatives
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
Chapter 3, Problem 52

In Exercises 51 and 52, find dp/dq.
q = (5p² + 2p)⁻³/²

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Identify the function q in terms of p: \( q = (5p^2 + 2p)^{-\frac{3}{2}} \). We need to find \( \frac{dp}{dq} \), which is the reciprocal of \( \frac{dq}{dp} \).
Use the chain rule to differentiate q with respect to p. The chain rule states that if you have a composite function \( f(g(x)) \), then \( \frac{d}{dx}f(g(x)) = f'(g(x)) \cdot g'(x) \).
Differentiate the outer function \( (u)^{-\frac{3}{2}} \) with respect to u, where \( u = 5p^2 + 2p \). The derivative is \( -\frac{3}{2}u^{-\frac{5}{2}} \).
Differentiate the inner function \( u = 5p^2 + 2p \) with respect to p. The derivative is \( 10p + 2 \).
Combine the derivatives using the chain rule: \( \frac{dq}{dp} = -\frac{3}{2}(5p^2 + 2p)^{-\frac{5}{2}} \cdot (10p + 2) \). Finally, find \( \frac{dp}{dq} \) by taking the reciprocal of \( \frac{dq}{dp} \).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Implicit Differentiation

Implicit differentiation is a technique used to differentiate equations where the dependent and independent variables are not explicitly separated. In this case, we need to differentiate the equation q = (5p² + 2p)⁻³/² with respect to p, treating q as a function of p. This method allows us to find the derivative dp/dq even when p is not isolated.
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Finding The Implicit Derivative

Chain Rule

The chain rule is a fundamental principle in calculus that allows us to differentiate composite functions. When differentiating q = (5p² + 2p)⁻³/², we apply the chain rule to handle the outer function (the exponent) and the inner function (the polynomial). This rule is essential for correctly calculating the derivative of complex expressions.
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Intro to the Chain Rule

Reciprocal Relationships in Derivatives

In calculus, the relationship between the derivatives of two variables can be expressed as dp/dq = 1/(dq/dp). This reciprocal relationship is useful when we need to find dp/dq after calculating dq/dp. Understanding this concept helps in switching between the derivatives of dependent and independent variables effectively.
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Derivatives
Related Practice
Textbook Question

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 ΔT, we can estimate the variation in g from the equation T = 2π(L/g)¹/² that relates T, g, and L.


a. With L held constant and g as the independent variable, calculate dT and use it to answer parts (b) and (c).

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Textbook Question

Find all points (x, y) on the graph of y = x/(x − 2) with tangent lines perpendicular to the line y = 2x + 3.

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Textbook Question

a. Find an equation for the line that is tangent to the curve y = x³ − 6x² + 5x at the origin.

[Technology Exercise] b. Graph the curve and tangent line together. The tangent line intersects the curve at another point. Use Zoom and Trace to estimate the point’s coordinates.

[Technology Exercise] c. Confirm your estimates of the coordinates of the second intersection point by solving the equations for the curve and tangent line simultaneously.

215
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Textbook Question

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 ΔT, we can estimate the variation in g from the equation T = 2π(L/g)¹/² that relates T, g, and L.


b. If g increases, will T increase or decrease? Will a pendulum clock speed up or slow down? Explain.

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Textbook Question

Find by implicit differentiation.

x²y² = 1

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Textbook Question

Assume that functions f and g are differentiable with f(1) = 2, f'(1) = −3, g(1) = 4, and g'(1) = −2. Find the equation of the line tangent to the graph of F(x) = f(x)g(x) at x = 1.

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