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Example Questions
Example Question #1 : Lines
What is the equation of the line tangent to f(x) = 4x3 – 2x2 + 4 at x = 5?
y = 280x – 946
None of the other answers
y = 220x – 550
y = 85x + 24
y = 44x + 245
y = 280x – 946
First, take the derivative of f(x). This is very easy:
f'(x) = 12x2 – 4x
Now, the slope of the tangent line at x = 5 is f'(5). Evaluated, this is: f'(5) = 12 * 5 * 5 – 4 * 5 = 300 – 20 = 280
Now, we must find the intersection point on the original line:
f(5) = 4 * 53 – 2 * 52 + 4 = 500 – 50 + 4 = 454
Therefore, the point of tangent intersection is (5,454).
Using the point-slope form of linear equations, we can find the line:
(y – 454) = 280(x – 5)
y – 454 = 280x – 1400
y = 280x – 946
Example Question #1 : Lines
Find the equation of the line tangent to
at the point .
The equation of the tangent line will have the form
, where is the slope of the line and .To find the slope, we need to evaluate the derivative at
:
Now that we have the slope, we can determine the equation of the tangent line using the point-slope formula:
Example Question #1 : How To Find Equation Of Line By Graphing Functions
Find the equation of the line tangent to
at .
To find the equation of the line at that point, you need two things: the slope at that point and the y adjustment of the function, in the form
, where m is the slope and is the y adjustment. To get the slope, find the derivative of and plug in the desired point for , giving us an answer of for the slope.
To find the y adjustment pick a point 0 in the original
function. For simplicity, let's plug in , which gives us a y of 1, so an easy point is . Next plug in those values into the equation of a line, . The new equation with all parameters plugged in is
Now you simply solve for
, which is .Final equation of the line tangent to
at isExample Question #1 : Equation Of Line
Find the equation of the line tangent to
at .
To get the slope, find the derivative of
and plug in the desired point for , giving us an answer of for the slope.
Remember that the derivative of
.
To find the
adjustment pick a point (for example) in the original function. For simplicity, let's plug in , which gives us a of , so an easy point is . Next plug in those values into the equation of a line, . The new equation with all parameters plugged in is
The coefficient in front of the
is the slope.Now you simply solve for
, which is .Final equation of the line tangent to
at is .Example Question #2 : How To Find Equation Of Line By Graphing Functions
Find the equation of the line tangent to
at .
The equation of the tangent line is
To find , the slope, calculate the derivative and plug in the desired point.
The next step is to choose a coordinate on the original
function. We can choose any value and calculate its value.Let's choose
.
The
value at this point is .Plugging in those values we can solve for
.
Solving for
we get = .
Example Question #1 : How To Find Equation Of Line By Graphing Functions
A function,
, is given by.
Find the line tangent to
at .
First we need to find the slope of
at . To do this we need the derivative of . To take the derivative we need to use the power rule for the first term and recognize that the derivative of sine is cosine.
At,
Now we need to know
.
Now we have a slope,
and a pointso we can use the point-slope formula to find the equation of the line.
Plugging in and rearranging we find
.
Example Question #4 : How To Find Equation Of Line By Graphing Functions
Let
.Find the equation for a line tangent to
when .
First, evaluate
when .
Thus, we need a line that contains the point
Next, find the derivative of
and evaluate it at .To find the derivative we will use the power rule,
.
This indicates that we need a line with a slope of 8.
In point-slope form,
, a line with the point and a slope of 8 will be:
Example Question #2 : Lines
What is the equation of the line tangent to
at ? Round to the nearest hundreth.
The tangent line to
at must have the same slope as .Applying the chain rule we get
.
Therefore the slope of the line is,
.
In addition, the tangent line touches the graph of
at . Since , the point lies on the line.Plugging in the slope and point we get
.Example Question #2 : Equation Of Line
Find the equation of the tangent line, where
, at .
In order to find the equation of the tangent line at
, we first find the slope.To do this we need to find
.
Since we have found
, now we simply plug in 1.
Now we need to plug in 1, into
, to find a point that the tangent line touches.
Now we can use point-slope form to figure out what the equation of the tangent line is at
.Remember that point-slope for is
where
and is the point where the tangent line touches , and is the slope of the tangent line.In our case,
, , and .
Thus our tangent line equation at
is.
Example Question #3 : Equation Of Line
Find the equation of the tangent line of
, at .
In order to find the equation of the tangent line at
, we first find the slope.To do this we need to find
using the power rule .
Since we have found
, now we simply plug in 1.
Now we need to plug in 1, into
, to find a point that the tangent line touches.
Now we can use point-slope form to figure out what the equation of the tangent line is at
.Remember that point-slope for is
where
and is the point where the tangent line touches , and is the slope of the tangent line.In our case,
, , and .
Thus our tangent line equation at
is.
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