AP Calculus AB: 3.3.1 The Derivative of the Reciprocal Function
The derivative of the reciprocal function To find the tangent line at a point, compute the derivative to get the slope, then use point-slope form with the given point.
derivative of the reciprocal function
The derivative of is . f(x) = x^-1 is f’(x) = -x^-2
To find the equation of a line tangent to a curve, take the derivative, evaluate the derivative at the point of tangency to find the slope, and substitute the slope and the point of tangency into the point-slope form of a line.
Key Terms
derivative of the reciprocal function
The derivative of is . f(x) = x^-1 is f’(x) = -x^-2
To find the equation of a line tangent to a curve, take the derivative, ...
note
The function f(x)=x^-1 is called the reciprocal function because for any value of x the function produces the reciprocal of x as its output...
Suppose f(x)=4/x. What is the slope of the line tangent to f when x=3?
−4/9
Find the derivative of f(x)=−1/√5 x.
f′(x)=1/√5 x^2
At what points does the equation of the line tangent to the curve y=1/x have a slope equal to −1?
(−1, −1) and (1, 1)
Find the equation of the line tangent to the curve y = 1 / (2x) when x = 1.
y = (−1/2) x + 1
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| Term | Definition |
|---|---|
derivative of the reciprocal function |
|
note |
|
Suppose f(x)=4/x. What is the slope of the line tangent to f when x=3? | −4/9 |
Find the derivative of f(x)=−1/√5 x. | f′(x)=1/√5 x^2 |
At what points does the equation of the line tangent to the curve y=1/x have a slope equal to −1? | (−1, −1) and (1, 1) |
Find the equation of the line tangent to the curve y = 1 / (2x) when x = 1. | y = (−1/2) x + 1 |
Suppose f (x) = −4 / x. Find the equation of the line tangent to f (x) at (4, −1). | y = x / 4 − 2 |
Find the derivative of f(x)=−1/√2 x +2x. | f′(x)=2+1/√2 x^2 |
Suppose f (x) = 6 / x. What is the slope of the line tangent to f when x = −2? | −3/2 |
Find the derivative of f(x)=1/4x. | f′(x)=−1/4x^2 |
Suppose a particle’s position is given by f (t) = −4 / t, where t is measured in seconds and f (t) is given in centimeters. What is the velocity of the particle when t = 1? | 4 cm / sec |
Find the equation of the line tangent to the curve y = 6 / x when x = 3. | y−2=−2/3x+2 |
Find the derivative of f(x)=2/3x. | f′(x)=−2/3x^2 |
Suppose f (x) = −2 / x. Find the equation of the line tangent to f (x) at (1, −2). | y = 2x − 4 |
Suppose a particle’s position is given by f (t) = −2 / t, where t is measured in seconds and f (t) is given in centimeters. At what time is the velocity of the particle equal to 4 cm / s? | t=1/√2 |
Find the derivative of f(x)=1/3x. | f′(x)=−1/3x^2 |
At what points does the equation of the line tangent to the curve y=1/x+3 have a slope equal to −1? | (−1, 2) and (1, 4) |
Suppose a particle’s position is given by f (t) = 2 / t, where t is measured in seconds and f (t) is given in centimeters. What is the velocity of the particle when t = 2? | −1/2 cm / s |
Suppose a particle’s position is given by f(t)=3/t,where t is measured in seconds and f(t) is given in centimeters. At what time is the velocity of the particle equal to −12? | t=1/2 |