AP Calculus BC : Computation of Derivatives

Study concepts, example questions & explanations for AP Calculus BC

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Example Questions

Example Question #71 : Computation Of Derivatives

What is the derivative of ?

Possible Answers:

Correct answer:

Explanation:

In order to find the derivative   of a polar equation , we must first find the derivative of with respect to  as follows:

We can then swap the given values of  and  into the equation of the derivative of an expression into polar form:

 

Using the trigonometric identity , we can deduce that . Swapping this into the denominator, we get:

Example Question #2 : Derivatives Of Parametric, Polar, And Vector Functions

Given that  . We define its gradient as :

Let  be given by:

 

What is the gradient of ?

Possible Answers:

Correct answer:

Explanation:

By definition, to find the gradient vector , we will have to find the gradient components. We know that the gradient components are that partial derivatives.

We know that in our case we have :

 

To see this, fix all other variables and assume that you have only  as the only variable.

Now we apply the given defintion , i.e,

with :

this gives us the solution .

 

Example Question #7 : Derivatives Of Parametric, Polar, And Vector Functions

Let .

We define the gradient of as:

Let .

Find the vector gradient.

Possible Answers:

Correct answer:

Explanation:

We note first that :

Using the Chain Rule where  is the only variable here.

Using the Chain Rule where  is the only variable here.

Continuing in this fashion we have:

Again using the Chain Rule and assuming that  is the variable and all the others are constant.

Now applying the given definition of the gradient we have the required result.

 

 

Example Question #3 : Derivatives Of Parametric, Polar, And Vector Functions

Let 

What is the derivative of ?

Possible Answers:

Correct answer:

Explanation:

To find the derivative of this vector, all we need to do is to differentiate each component with respect to t.

Use the Power Rule and the Chain Rule when differentiating.

  is the derivative of the first component.

 of the second component.

 is the derivative of the last component . we obtain then:

Example Question #3 : Derivatives Of Parametric, Polar, And Vector Functions

Possible Answers:

Correct answer:

Explanation:

In general:

If ,

then 

Derivative rules that will be needed here:

  • Taking a derivative on a term, or using the power rule, can be done by doing the following:
  • When taking derivatives of sums, evaluate with the sum rule which states that the derivative of the sum is the same as the sum of the derivative of each term: 
  • Special rule when differentiating an exponential function:  , where k is a constant.

In this problem, 

 

Put it all together to get 

Example Question #174 : Derivatives

Given the parametric curve

Evaluate  when .

Possible Answers:

Correct answer:

Explanation:

To find , we can use the formula .

.

And .

Hence .

Plugging in , we get

Example Question #72 : Computation Of Derivatives

Find  of the following function:

Possible Answers:

Correct answer:

Explanation:

To find the derivative of the parametric function, we must use the following:

So, we must take the derivative of each component with respect to t:

The derivative was found using the following rules:

This derivative was found using the following rule:

Dividing the two and factoring, we get

Example Question #73 : Computation Of Derivatives

Find , where

Possible Answers:

Correct answer:

Explanation:

To find the derivative of x with respect to t, we must differentiate both sides of the parametric equation with respect to t:

The derivatives were found using the following rules:

Note that the chain rule was used when taking the derivative of .

Solving, we get

Example Question #181 : Derivatives

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A particle moves around the xy plane such that its position as a function of time is given by the parametric function:

 .

What is the slope, , of the particle's trajectory when ?

Possible Answers:

Correct answer:

Explanation:

Evaluate the slope as

 .

We have

and

so

Evaluating this when  gives

.

Remark: This curve is one example from family of curves called Lissajous figures, which can be observed on oscilloscopes.

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