AP Calculus BC : Computation of Derivatives

Study concepts, example questions & explanations for AP Calculus BC

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Example Questions

Example Question #22 : Chain Rule And Implicit Differentiation

Find  from the following equation:

, where  is a function of x.

Possible Answers:

Correct answer:

Explanation:

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

The derivatives were found using the following rules:

Solving for , we get

Note that the chain rule was used because of the exponential and because  is a function of x.

Example Question #61 : Computation Of Derivatives

Find the first derivative of the following function:

Possible Answers:

Correct answer:

Explanation:

The derivative of the function is equal to

and was found using the following rules:

Note that the chain rule was used on the secant function as well as the natural logarithm function. 

Example Question #21 : Chain Rule And Implicit Differentiation

Find :

Possible Answers:

Correct answer:

Explanation:

To determine , we must take the derivative of both sides of the equation with respect to x:

The derivatives were found using the following rules:

Rearranging and solving for , we get

 

Example Question #21 : Chain Rule And Implicit Differentiation

A curve in the xy plane is given implictly by

.

Calculate the slope of the line tangent to the curve at the point .

Possible Answers:

Correct answer:

Explanation:

Differentiate both sides with respect to  using the chain rule and the product rule as:

Then solve for  as if it were our unknown:

.

Finally, evaluate  at the point  to obtain the slope through that point:

.

 

Example Question #21 : Chain Rule And Implicit Differentiation

Screen shot 2016 03 31 at 11.11.35 am

Figure. Squircle of "radius" 1

squircle is a curve in the xy plane that appears like a rounded square, but whose points satisfy the following equation (analogous to the Pythagorean theorem for a circle)

where the constant  is the "radius" of the squircle.

Using implicit differentiation, obtain an expression for  as a function of both  and .

Possible Answers:

Correct answer:

Explanation:

Differentiate both sides of the equation with respect to , using the chain rule on the  term:

Then solve for  as if it were our unknown:

.

Comparing this to the figure, our answer makes sense, because the slope of the squircle is  wherever  (as it crosses the  axis) and undefined (vertical) wherever  (as it crosses the  axis). Lastly, we note that in the first quadrant (where  and ), the slope of the squircle is negative, which is exactly what we observe in the figure.

Example Question #1 : Derivatives Of Parametrics

Find the derivative of the following set of parametric equations:

Possible Answers:

Correct answer:

Explanation:

We start by taking the derivative of x and y with respect to t, as both of the equations are only in terms of this variable:

The problem asks us to find the derivative of the parametric equations, dy/dx, and we can see from the work below that the dt term is cancelled when we divide dy/dt by dx/dt, leaving us with dy/dx:

So now that we know dx/dt and dy/dt, all we must do to find the derivative of our parametric equations is divide dy/dt by dx/dt:

Example Question #9 : Derivatives Of Parametrics

Solve for  if  and .

Possible Answers:

None of the above

Correct answer:

Explanation:

We can determine that   since the  terms will cancel out in the division process.

Since  and , we can use the Power Rule

 for all  to derive

and  .

Thus:

.

Example Question #1 : Derivatives Of Parametric, Polar, And Vector Functions

Find the derivative of the following polar equation:

Possible Answers:

Correct answer:

Explanation:

Our first step in finding the derivative dy/dx of the polar equation is to find the derivative of r with respect to . This gives us:

Now that we know dr/d, we can plug this value into the equation for the derivative of an expression in polar form:

Simplifying the equation, we get our final answer for the derivative of r:

Example Question #1 : Derivatives Of Parametric, Polar, And Vector Functions

Find the derivative  of the polar function .

Possible Answers:

Correct answer:

Explanation:

The derivative of a polar function is found using the formula

The only unknown piece is . Recall that the derivative of a constant is zero, and that 

, so

Substiting  this into the derivative formula, we find

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

Find the first derivative of the polar function 

.

Possible Answers:

Correct answer:

Explanation:

In general, the dervative of a function in polar coordinates can be written as

.

Therefore, we need to find , and then substitute  into the derivative formula.

To find , the chain rule, 

, is necessary.

We also need to know that 

.

Therefore,

.  

Substituting  into the derivative formula yields

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