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The chain rule

Spotting that a formula is a composition f(g(x)) and differentiating it as the outer rate times the inner rate rather than term by term.

Active Calculus, The chain rule

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6 exercises

Activity 2.5.2

For each function given below, identify an inner function gg and outer function ff to write the function in the form f(g(x))f(g(x)). Determine f′(x)f'(x), g′(x)g'(x), and f′(g(x))f'(g(x)), and then apply the chain rule to determine the derivative of the given function.

  1. h(x)=cos⁡(x4)h(x) = \cos(x^4)

  2. p(x)=tan⁡(x)p(x) = \sqrt{ \tan(x) }

  3. s(x)=2sin⁡(x)s(x) = 2^{\sin(x)}

  4. z(x)=cot⁡5(x)z(x) = \cot^5(x)

  5. m(x)=(sec⁡(x)+ex)9m(x) = (\sec(x) + e^x)^9

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Activity 2.5.3

For each of the following functions, find the function's derivative. State the rule(s) you use, label relevant derivatives appropriately, and be sure to clearly identify your overall answer.

  1. p(r)=4r6+2erp(r) = 4\sqrt{r^6 + 2e^r}

  2. m(v)=sin⁡(v2)cos⁡(v3)m(v) = \sin(v^2) \cos(v^3)

  3. h(y)=cos⁡(10y)e4y+1h(y) = \frac{\cos(10y)}{e^{4y}+1}

  4. s(z)=2z2sec⁡(z)s(z) = 2^{z^2 \sec (z)}

  5. c(x)=sin⁡(ex2)c(x) = \sin(e^{x^2})

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Activity 2.5.4

Use known derivative rules, including the chain rule, as needed to respond to each of the following prompts.

  1. Find an equation for the tangent line to the curve y=ex+3y= \sqrt{e^x + 3} at the point where x=0x=0.

  2. If s(t)=1(t2+1)3\displaystyle s(t) = \frac{1}{(t^2+1)^3} represents the position function of a particle moving horizontally along an axis at time tt (where ss is measured in inches and tt in seconds), find the particle's instantaneous velocity at t=1t=1. Is the particle moving…

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Exercise 11

Consider the basic functions f(x)=x3f(x) = x^3 and g(x)=sin⁡(x)g(x) = \sin(x).

  1. Let h(x)=f(g(x))h(x) = f(g(x)). Find the exact instantaneous rate of change of hh at the point where x=π4x = \frac{\pi}{4}.

  2. Which function is changing most rapidly at x=0.25x = 0.25: h(x)=f(g(x))h(x) = f(g(x)) or r(x)=g(f(x))r(x) = g(f(x))? Why?

  3. Let h(x)=f(g(x))h(x) = f(g(x)) and r(x)=g(f(x))r(x) = g(f(x)). Which of these functions has a derivative that is periodic? Why?

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Exercise 12

Let u(x)u(x) be a differentiable function. For each of the following functions, determine the derivative. Each response will involve uu and/or u′u'.

  1. p(x)=eu(x)p(x) = e^{u(x)}

  2. q(x)=u(ex)q(x) = u(e^x)

  3. r(x)=cot⁡(u(x))r(x) = \cot(u(x))

  4. s(x)=u(cot⁡(x))s(x) = u(\cot(x))

  5. a(x)=u(x4)a(x) = u(x^4)

  6. b(x)=(u(x))4b(x) = (u(x))^4

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Exercise 14

If a spherical tank of radius 4 feet has hh feet of water present in the tank, then the volume of water in the tank is given by the formula .

  1. At what instantaneous rate is the volume of water in the tank changing with respect to the height of the water at the instant h=1h = 1? What are the units on this quantity?

  2. Now suppose that the height of water in the tank is being regulated by an inflow and outflow (e…

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Adapted from Active Calculus © 2012–2025 Matthew Boelkins. Licensed under CC BY-SA 4.0. Source: Active Calculus. Imported at revision dc86ba3.