<< Chapter < Page Chapter >> Page >

Find the derivative of f ( x ) = 2 tan x 3 cot x .

f ( x ) = 2 sec 2 x + 3 csc 2 x

Got questions? Get instant answers now!

Find the slope of the line tangent to the graph of f ( x ) = tan x at x = π 6 .

4 3

Got questions? Get instant answers now!

Higher-order derivatives

The higher-order derivatives of sin x and cos x follow a repeating pattern. By following the pattern, we can find any higher-order derivative of sin x and cos x .

Finding higher-order derivatives of y = sin x

Find the first four derivatives of y = sin x .

Each step in the chain is straightforward:

y = sin x d y d x = cos x d 2 y d x 2 = sin x d 3 y d x 3 = cos x d 4 y d x 4 = sin x .
Got questions? Get instant answers now!
Got questions? Get instant answers now!

For y = cos x , find d 4 y d x 4 .

cos x

Got questions? Get instant answers now!

Using the pattern for higher-order derivatives of y = sin x

Find d 74 d x 74 ( sin x ) .

We can see right away that for the 74th derivative of sin x , 74 = 4 ( 18 ) + 2 , so

d 74 d x 74 ( sin x ) = d 72 + 2 d x 72 + 2 ( sin x ) = d 2 d x 2 ( sin x ) = sin x .
Got questions? Get instant answers now!
Got questions? Get instant answers now!

For y = sin x , find d 59 d x 59 ( sin x ) .

cos x

Got questions? Get instant answers now!

An application to acceleration

A particle moves along a coordinate axis in such a way that its position at time t is given by s ( t ) = 2 sin t . Find v ( π / 4 ) and a ( π / 4 ) . Compare these values and decide whether the particle is speeding up or slowing down.

First find v ( t ) = s ( t ) :

v ( t ) = s ( t ) = cos t .

Thus,

v ( π 4 ) = 1 2 .

Next, find a ( t ) = v ( t ) . Thus, a ( t ) = v ( t ) = sin t and we have

a ( π 4 ) = 1 2 .

Since v ( π 4 ) = 1 2 < 0 and a ( π 4 ) = 1 2 > 0 , we see that velocity and acceleration are acting in opposite directions; that is, the object is being accelerated in the direction opposite to the direction in which it is travelling. Consequently, the particle is slowing down.

Got questions? Get instant answers now!
Got questions? Get instant answers now!

A block attached to a spring is moving vertically. Its position at time t is given by s ( t ) = 2 sin t . Find v ( 5 π 6 ) and a ( 5 π 6 ) . Compare these values and decide whether the block is speeding up or slowing down.

v ( 5 π 6 ) = 3 < 0 and a ( 5 π 6 ) = −1 < 0 . The block is speeding up.

Got questions? Get instant answers now!

Key concepts

  • We can find the derivatives of sin x and cos x by using the definition of derivative and the limit formulas found earlier. The results are
    d d x sin x = cos x d d x cos x = sin x .
  • With these two formulas, we can determine the derivatives of all six basic trigonometric functions.

Key equations

  • Derivative of sine function
    d d x ( sin x ) = cos x
  • Derivative of cosine function
    d d x ( cos x ) = sin x
  • Derivative of tangent function
    d d x ( tan x ) = sec 2 x
  • Derivative of cotangent function
    d d x ( cot x ) = csc 2 x
  • Derivative of secant function
    d d x ( sec x ) = sec x tan x
  • Derivative of cosecant function
    d d x ( csc x ) = csc x cot x

For the following exercises, find d y d x for the given functions.

y = x 2 sec x + 1

d y d x = 2 x sec x tan x

Got questions? Get instant answers now!

y = x 2 cot x

d y d x = 2 x cot x x 2 csc 2 x

Got questions? Get instant answers now!

y = sec x x

d y d x = x sec x tan x sec x x 2

Got questions? Get instant answers now!

y = ( x + cos x ) ( 1 sin x )

d y d x = ( 1 sin x ) ( 1 sin x ) cos x ( x + cos x )

Got questions? Get instant answers now!

y = 1 cot x 1 + cot x

d y d x = 2 csc 2 x ( 1 + cot x ) 2

Got questions? Get instant answers now!

For the following exercises, find the equation of the tangent line to each of the given functions at the indicated values of x . Then use a calculator to graph both the function and the tangent line to ensure the equation for the tangent line is correct.

[T] f ( x ) = sin x , x = 0

y = x
The graph shows negative sin(x) and the straight line T(x) with slope −1 and y intercept 0.

Got questions? Get instant answers now!

[T] f ( x ) = csc x , x = π 2

Got questions? Get instant answers now!

[T] f ( x ) = 1 + cos x , x = 3 π 2

y = x + 2 3 π 2
The graph shows the cosine function shifted up one and has the straight line T(x) with slope 1 and y intercept (2 – 3π)/2.

Got questions? Get instant answers now!

[T] f ( x ) = sec x , x = π 4

Got questions? Get instant answers now!

[T] f ( x ) = x 2 tan x x = 0

y = x
The graph shows the function as starting at (−1, 3), decreasing to the origin, continuing to slowly decrease to about (1, −0.5), at which point it decreases very quickly.

Got questions? Get instant answers now!

[T] f ( x ) = 5 cot x x = π 4

Got questions? Get instant answers now!

For the following exercises, find d 2 y d x 2 for the given functions.

y = x sin x cos x

3 cos x x sin x

Got questions? Get instant answers now!

y = x 1 2 sin x

1 2 sin x

Got questions? Get instant answers now!

y = 2 csc x

csc ( x ) ( 3 csc 2 ( x ) 1 + cot 2 ( x ) )

Got questions? Get instant answers now!

Find all x values on the graph of f ( x ) = −3 sin x cos x where the tangent line is horizontal.

( 2 n + 1 ) π 4 , where n is an integer

Got questions? Get instant answers now!

Find all x values on the graph of f ( x ) = x 2 cos x for 0 < x < 2 π where the tangent line has slope 2.

Got questions? Get instant answers now!

Let f ( x ) = cot x . Determine the points on the graph of f for 0 < x < 2 π where the tangent line(s) is (are) parallel to the line y = −2 x .

( π 4 , 1 ) , ( 3 π 4 , −1 )

Got questions? Get instant answers now!

[T] A mass on a spring bounces up and down in simple harmonic motion, modeled by the function s ( t ) = −6 cos t where s is measured in inches and t is measured in seconds. Find the rate at which the spring is oscillating at t = 5 s.

Got questions? Get instant answers now!

Let the position of a swinging pendulum in simple harmonic motion be given by s ( t ) = a cos t + b sin t . Find the constants a and b such that when the velocity is 3 cm/s, s = 0 and t = 0 .

a = 0 , b = 3

Got questions? Get instant answers now!

After a diver jumps off a diving board, the edge of the board oscillates with position given by s ( t ) = −5 cos t cm at t seconds after the jump.

  1. Sketch one period of the position function for t 0 .
  2. Find the velocity function.
  3. Sketch one period of the velocity function for t 0 .
  4. Determine the times when the velocity is 0 over one period.
  5. Find the acceleration function.
  6. Sketch one period of the acceleration function for t 0 .
Got questions? Get instant answers now!

The number of hamburgers sold at a fast-food restaurant in Pasadena, California, is given by y = 10 + 5 sin x where y is the number of hamburgers sold and x represents the number of hours after the restaurant opened at 11 a.m. until 11 p.m., when the store closes. Find y and determine the intervals where the number of burgers being sold is increasing.

y = 5 cos ( x ) , increasing on ( 0 , π 2 ) , ( 3 π 2 , 5 π 2 ) , and ( 7 π 2 , 12 )

Got questions? Get instant answers now!

[T] The amount of rainfall per month in Phoenix, Arizona, can be approximated by y ( t ) = 0.5 + 0.3 cos t , where t is months since January. Find y and use a calculator to determine the intervals where the amount of rain falling is decreasing.

Got questions? Get instant answers now!

For the following exercises, use the quotient rule to derive the given equations.

d d x ( cot x ) = csc 2 x

Got questions? Get instant answers now!

d d x ( sec x ) = sec x tan x

Got questions? Get instant answers now!

d d x ( csc x ) = csc x cot x

Got questions? Get instant answers now!

Use the definition of derivative and the identity

cos ( x + h ) = cos x cos h sin x sin h to prove that d ( cos x ) d x = sin x .

Got questions? Get instant answers now!

For the following exercises, find the requested higher-order derivative for the given functions.

d 3 y d x 3 of y = 3 cos x

3 sin x

Got questions? Get instant answers now!

d 2 y d x 2 of y = 3 sin x + x 2 cos x

Got questions? Get instant answers now!

d 4 y d x 4 of y = 5 cos x

5 cos x

Got questions? Get instant answers now!

d 2 y d x 2 of y = sec x + cot x

Got questions? Get instant answers now!

d 3 y d x 3 of y = x 10 sec x

720 x 7 5 tan ( x ) sec 3 ( x ) tan 3 ( x ) sec ( x )

Got questions? Get instant answers now!

Questions & Answers

Examine the distinction between theory of comparative cost Advantage and theory of factor proportion
Fatima Reply
What is inflation
Bright Reply
a general and ongoing rise in the level of prices in an economy
AI-Robot
What are the factors that affect demand for a commodity
Florence Reply
price
Kenu
differentiate between demand and supply giving examples
Lambiv Reply
differentiated between demand and supply using examples
Lambiv
what is labour ?
Lambiv
how will I do?
Venny Reply
how is the graph works?I don't fully understand
Rezat Reply
information
Eliyee
devaluation
Eliyee
t
WARKISA
hi guys good evening to all
Lambiv
multiple choice question
Aster Reply
appreciation
Eliyee
explain perfect market
Lindiwe Reply
In economics, a perfect market refers to a theoretical construct where all participants have perfect information, goods are homogenous, there are no barriers to entry or exit, and prices are determined solely by supply and demand. It's an idealized model used for analysis,
Ezea
What is ceteris paribus?
Shukri Reply
other things being equal
AI-Robot
When MP₁ becomes negative, TP start to decline. Extuples Suppose that the short-run production function of certain cut-flower firm is given by: Q=4KL-0.6K2 - 0.112 • Where is quantity of cut flower produced, I is labour input and K is fixed capital input (K-5). Determine the average product of lab
Kelo
Extuples Suppose that the short-run production function of certain cut-flower firm is given by: Q=4KL-0.6K2 - 0.112 • Where is quantity of cut flower produced, I is labour input and K is fixed capital input (K-5). Determine the average product of labour (APL) and marginal product of labour (MPL)
Kelo
yes,thank you
Shukri
Can I ask you other question?
Shukri
what is monopoly mean?
Habtamu Reply
What is different between quantity demand and demand?
Shukri Reply
Quantity demanded refers to the specific amount of a good or service that consumers are willing and able to purchase at a give price and within a specific time period. Demand, on the other hand, is a broader concept that encompasses the entire relationship between price and quantity demanded
Ezea
ok
Shukri
how do you save a country economic situation when it's falling apart
Lilia Reply
what is the difference between economic growth and development
Fiker Reply
Economic growth as an increase in the production and consumption of goods and services within an economy.but Economic development as a broader concept that encompasses not only economic growth but also social & human well being.
Shukri
production function means
Jabir
What do you think is more important to focus on when considering inequality ?
Abdisa Reply
any question about economics?
Awais Reply
sir...I just want to ask one question... Define the term contract curve? if you are free please help me to find this answer 🙏
Asui
it is a curve that we get after connecting the pareto optimal combinations of two consumers after their mutually beneficial trade offs
Awais
thank you so much 👍 sir
Asui
In economics, the contract curve refers to the set of points in an Edgeworth box diagram where both parties involved in a trade cannot be made better off without making one of them worse off. It represents the Pareto efficient allocations of goods between two individuals or entities, where neither p
Cornelius
In economics, the contract curve refers to the set of points in an Edgeworth box diagram where both parties involved in a trade cannot be made better off without making one of them worse off. It represents the Pareto efficient allocations of goods between two individuals or entities,
Cornelius
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Calculus volume 1. OpenStax CNX. Feb 05, 2016 Download for free at http://cnx.org/content/col11964/1.2
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Calculus volume 1' conversation and receive update notifications?

Ask