Section 1.3
Applications of Derivatives
Goals:
1 Write the equation of a tangent line.
2 Identify local maximums and minimums.
3 Use the Extreme Value Theorem to find minimums and maximums.
4 Use l’Hˆopital’s rule to compute limits.
This section reviews the most important applications of the derivative.
Application 1.3.1
The Tangent Line to a Graph
Given a function f (x), the derivative f
(a) is the slope of the line tangent to y = f(x) at (a, f(a)).
Formula
The equation of the tangent line to y = f(x) at x = a in point-slope form is:
y f(a) = f
(a)(x a)
We can rewrite the tangent line as a function of x. We call this a linearization, because this function
is linear, but it approximates the value of f(x) for x near a.
Formula
The linearization of y = f(x) at x = a is the function:
L(x) = f(a) + f
(a)(x a)
If we want to emphasize the change in x and y instead of their actual values we can use differential
notation:
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