Differential of a Function
Solved Problems
Example 9.
Find the differential of the function
Solution.
We calculate the derivative using the product and chain rule:
The differential of the function is written as
Example 10.
Find the differential of the function
Solution.
First we determine the derivative using the chain rule:
Apply the double angle identity
Hence
The differential of a function is written in the form
Then
Example 11.
Find the differential of
Solution.
Substitute the values of
Example 12.
Find the differential of the function
Solution.
Differentiate the given function:
At the point
Hence, the differential of the function at this point is
Example 13.
Use differential to approximate the change in
Solution.
We calculate the differential of the function by the formula
The derivative is given by
At the initial point
Calculate the differential of the independent variable:
Then the differential
The approximate value of the function at
Example 14.
Calculate the increment and differential of the function
Solution.
First we compute the increment of the function:
At the same values of
Example 15.
Find the differential of the function
Solution.
Take the derivative of the function:
At the point
Then
Example 16.
Calculate the differential of the function
Solution.
Take the derivative:
At
So the differential
Example 17.
Find the differential of the function
Solution.
Using the differentiation rules, we obtain:
Example 18.
Find the differential of the function
Solution.
where
Example 19.
The function
Determine the derivative of the implicit function. Differentiating both sides with respect to
At the point
The differential at this point is respectively written as
Example 20.
The function
Solution.
We differentiate both sides of the equation with respect to
Calculate the value of the derivative at the given point
The differential of the function at this point is written in the following form:
Example 21.
Suppose that a force
Solution.
Note that
We evaluate the differential
and
then
Similarly we can find that
Example 22.
A body is moving through a liquid. The resistance force
Solution.
It is easy to see that
We estimate the approximate value of the force using the differential:
Take the derivative:
so when
Assuming
Similarly, we can find the differential for
Thus, the resistance force takes on values in the interval
Example 23.
The function
Solution.
We calculate the corresponding values of the parameter
Make sure that the value
When
Thus, the differential of the function at the point
Example 24.
The function
Solution.
First we determine the value of the parameter
Check the value of
Find the derivative of the parametric function:
When
Consequently, the differential of the function at the point
Example 25.
Given the composite function
Solution.
We write the differential of the "outer" function:
Similarly, we find the differential of the "inner" function:
Substituting the expression for