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Derivatives of powers of a function have several uses, as we will see once we get to applications of derivatives. To establish a pattern for this type of derivative, we’ll consider the functions ,
, and
, where f is being used to represent some function
.
First, consider the function .
By the product rule, we have:
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Now consider the function .
By the product rule again, we have:
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Apply the product rule. |
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Replace ![]() ![]() |
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Combine ![]() |
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Combine like terms. |
Next, consider .
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Apply the product rule. |
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Replace ![]() ![]() |
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Combine ![]() |
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Combine like terms. |
By looking at this pattern, it seems as though the derivative of is
(looks like the power rule), but then also multiplied by
.
EXAMPLE
Earlier, we found the derivative of
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Apply the power rule. |
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Combine and eliminate parentheses. |
EXAMPLE
Find the derivative of the function
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Apply the power rule. |
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Combine ![]() |
Remember the other expressions that can be written as powers of x.
EXAMPLE
Find the derivative of the function
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Rewrite the radical using a power. |
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Use the power rule for derivatives. |
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Rewrite with nonnegative exponents. |
EXAMPLE
Find the derivative of the function
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Rewrite so that the power rule can be used. |
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Apply the power rule. |
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Rearrange the factors. |
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Rewrite with nonnegative exponents. |
EXAMPLE
The distance (measured in feet) from a moving camera to an object positioned at the point (1, 4) is given by the function
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Write the radical as ![]() |
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Apply the power rule. |
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Rearrange the terms. |
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Distribute ![]() |
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Rewrite with nonnegative exponents. |
Now that we are building up our derivative rules, we can find derivatives of more complex functions.
EXAMPLE
Find the derivative of the function
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Rewrite the square root as ![]() |
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Apply the product rule. |
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Rewrite with positive exponents. |
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The common denominator is ![]() Write ![]() |
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Perform multiplication. ![]() |
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Distribute ![]() |
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Combine the numerators. |
Source: THIS TUTORIAL HAS BEEN ADAPTED FROM CHAPTER 2 OF "CONTEMPORARY CALCULUS" BY DALE HOFFMAN. ACCESS FOR FREE AT WWW.CONTEMPORARYCALCULUS.COM. LICENSE: CREATIVE COMMONS ATTRIBUTION 3.0 UNITED STATES.