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2.10 Finding the Derivatives of Tangent, Cotangent, Secant, and/or Cosecant Functions

2 min readfebruary 15, 2024

Attend a live cram event

Review all units live with expert teachers & students

Welcome back to AP Calculus with Fiveable! Now that you’ve mastered finding derivatives of trigonometric functions sinx\sin x and cosx\cos x, let’s cover the rest! Remembering these rules is key to simplifying your calculus journey. 🌟

💫 Derivatives of Advanced Trigonometric Functions

First, let’s have a glance at a summary table for quick reference.

FunctionDerivative
Tangent Function: f(x)=tanxf(x) =\tan xf(x)=sec2xf'(x)=\sec^2 x
Cotangent Function: g(x)=cotxg(x)=\cot xg(x)=csc2xg'(x)=-\csc^2 x
Secant Function: h(x)=secxh(x)= \sec xh(x)=secxtanxh'(x)= \sec x \tan x
Cosecant Function: k(x)=cscxk(x)=\csc xk(x)=cscxcotxk'(x) = -\csc x \cot x

It's important to note that these are only valid for angles in radians, not degrees.

Derivative of tanx\tan x

The derivative of tanx\tan x is sec2x\sec^2 x. Let’s consider an example:

f(x)=3tanx+2x2f(x)=3\tan x+2x^2

To find the derivative of this equation, differentiate 3tanx3\tan x and 2x22x^2 individually.

Since the derivative of tanx\tan x is sec2x\sec^2 x, the derivative of the first part is 3sec2x3\sec^2 x. The derivative of 2x22x^2 is 4x4x. Hence, f(x)=3sec2x+4xf'(x) = 3\sec^2 x + 4x.

Derivative of cotx\cot x

The derivative of cotx\cot x is csc2x-\csc^2 x. For example:

f(x)=5cotx+xf(x)=5\cot x+x

We again have to differentiate the two terms separately! The derivative of cotx\cot x is csc2x-\csc^2 x, so the derivative of the first term is 5csc2x-5\csc^2 x. The derivative of xx is 11. Therefore, f(x)=5csc2x+1f'(x) = -5\csc^2 x + 1 or f(x)=15csc2xf'(x)=1-5\csc^2 x.

Derivative of secx\sec x

The derivative of secx\sec x is secxtanx\sec x \tan x. As an example:

f(x)=2secx+3x3f(x)=2\sec x+3x^3

Knowing the above trig derivative rule, the derivative of the first term is 2secxtanx2\sec x \tan x. The derivative of 3x33x^3 is 9x29x^2. Thus, f(x)=2secxtanx+9x2f'(x) = 2\sec x \tan x + 9x^2.

Derivative of cscx\csc x

Last but not least, the derivative of cscx\csc x is cscxcotx-\csc x \cot x. For instance:

f(x)=4cscx+7x2f(x)=4\csc x+7x^2

The derivative of the first part is 4cscxcotx-4\csc x \cot x. The derivative of 7x27x^2 is 14x14x. Therefore, f(x)=4cscxcotx+14xf'(x) = -4\csc x \cot x + 14x.


🏋️‍♂️ Practice Problems

Here are a couple of questions for you to get the concepts down!

❓ Advanced Trig Derivative Practice Questions

Find the derivatives for the following problems.

  1. f(x)=2tan(x)+sec(x)f(x) = 2 \tan(x) + \sec(x)
  2. f(x)=cot(x)csc(x)f(x) = \frac{\cot(x)}{\csc(x)}
  3. g(x)=tan2(6x)g(x) =\tan^2(6x)
  4. h(x)=5cot(x)h(x) = 5\cot(x)

💡 Before we reveal the answers, remember to use the chain rule, sum rule, and quotient rules.

🤔 Advanced Trig Derivative Practice Solutions

  1. f(x)=2sec2(x)+sec(x)tan(x)f'(x) = 2 \sec^2(x) + \sec(x) \tan(x)
  2. f(x)=csc2(x)f'(x)=−\csc^2(x)
  3. g(x)=2tan(6x)(1cos2(6x))g'(x)=2\tan(6x)(\frac{1}{\cos^2(6x)})
  4. h(x)=5csc2(x)h'(x)=−5\csc^2(x)

🌟 Closing

Practice these rules, and you’ll soon find them as intuitive as the basic derivatives! Keep up the great work. 🌈

Key Terms to Review (10)

(-csc(x)cot(x))

: The term (-csc(x)cot(x)) represents the product of the cosecant and cotangent functions of an angle x, with a negative sign in front. It is commonly used in trigonometric identities and calculations.

(-csc^2(x))

: The term (-csc^2(x)) represents the derivative of the cosecant function squared. It measures how fast the cosecant function is changing at a specific point on its graph, multiplied by -1.

(cot(x))'

: The term (cot(x))' represents the derivative of the cotangent function. It measures how fast the cotangent function is changing at a specific point on its graph.

(sec^2(x))

: The term (sec^2(x)) represents the derivative of the secant function. It measures how fast the secant function is changing at a specific point on its graph.

Chain Rule

: The chain rule is a formula used to find the derivative of a composition of two or more functions. It states that the derivative of a composite function is equal to the derivative of the outermost function times the derivative of the innermost function.

Cotangent

: Cotangent is one of six trigonometric ratios used in right triangles. It represents the ratio between adjacent side length and opposite side length in relation to an acute angle.

Derivatives

: Derivatives are the rates at which quantities change. They measure how a function behaves as its input (x-value) changes.

sec(x)'

: The derivative of sec(x), which represents the rate of change of the secant function with respect to x.

Secant

: The secant of an angle in a right triangle is the ratio of the length of the hypotenuse to the length of the adjacent side.

Tangent

: A tangent line is a straight line that touches a curve at only one point and has the same slope as the curve at that point.

2.10 Finding the Derivatives of Tangent, Cotangent, Secant, and/or Cosecant Functions

2 min readfebruary 15, 2024

Attend a live cram event

Review all units live with expert teachers & students

Welcome back to AP Calculus with Fiveable! Now that you’ve mastered finding derivatives of trigonometric functions sinx\sin x and cosx\cos x, let’s cover the rest! Remembering these rules is key to simplifying your calculus journey. 🌟

💫 Derivatives of Advanced Trigonometric Functions

First, let’s have a glance at a summary table for quick reference.

FunctionDerivative
Tangent Function: f(x)=tanxf(x) =\tan xf(x)=sec2xf'(x)=\sec^2 x
Cotangent Function: g(x)=cotxg(x)=\cot xg(x)=csc2xg'(x)=-\csc^2 x
Secant Function: h(x)=secxh(x)= \sec xh(x)=secxtanxh'(x)= \sec x \tan x
Cosecant Function: k(x)=cscxk(x)=\csc xk(x)=cscxcotxk'(x) = -\csc x \cot x

It's important to note that these are only valid for angles in radians, not degrees.

Derivative of tanx\tan x

The derivative of tanx\tan x is sec2x\sec^2 x. Let’s consider an example:

f(x)=3tanx+2x2f(x)=3\tan x+2x^2

To find the derivative of this equation, differentiate 3tanx3\tan x and 2x22x^2 individually.

Since the derivative of tanx\tan x is sec2x\sec^2 x, the derivative of the first part is 3sec2x3\sec^2 x. The derivative of 2x22x^2 is 4x4x. Hence, f(x)=3sec2x+4xf'(x) = 3\sec^2 x + 4x.

Derivative of cotx\cot x

The derivative of cotx\cot x is csc2x-\csc^2 x. For example:

f(x)=5cotx+xf(x)=5\cot x+x

We again have to differentiate the two terms separately! The derivative of cotx\cot x is csc2x-\csc^2 x, so the derivative of the first term is 5csc2x-5\csc^2 x. The derivative of xx is 11. Therefore, f(x)=5csc2x+1f'(x) = -5\csc^2 x + 1 or f(x)=15csc2xf'(x)=1-5\csc^2 x.

Derivative of secx\sec x

The derivative of secx\sec x is secxtanx\sec x \tan x. As an example:

f(x)=2secx+3x3f(x)=2\sec x+3x^3

Knowing the above trig derivative rule, the derivative of the first term is 2secxtanx2\sec x \tan x. The derivative of 3x33x^3 is 9x29x^2. Thus, f(x)=2secxtanx+9x2f'(x) = 2\sec x \tan x + 9x^2.

Derivative of cscx\csc x

Last but not least, the derivative of cscx\csc x is cscxcotx-\csc x \cot x. For instance:

f(x)=4cscx+7x2f(x)=4\csc x+7x^2

The derivative of the first part is 4cscxcotx-4\csc x \cot x. The derivative of 7x27x^2 is 14x14x. Therefore, f(x)=4cscxcotx+14xf'(x) = -4\csc x \cot x + 14x.


🏋️‍♂️ Practice Problems

Here are a couple of questions for you to get the concepts down!

❓ Advanced Trig Derivative Practice Questions

Find the derivatives for the following problems.

  1. f(x)=2tan(x)+sec(x)f(x) = 2 \tan(x) + \sec(x)
  2. f(x)=cot(x)csc(x)f(x) = \frac{\cot(x)}{\csc(x)}
  3. g(x)=tan2(6x)g(x) =\tan^2(6x)
  4. h(x)=5cot(x)h(x) = 5\cot(x)

💡 Before we reveal the answers, remember to use the chain rule, sum rule, and quotient rules.

🤔 Advanced Trig Derivative Practice Solutions

  1. f(x)=2sec2(x)+sec(x)tan(x)f'(x) = 2 \sec^2(x) + \sec(x) \tan(x)
  2. f(x)=csc2(x)f'(x)=−\csc^2(x)
  3. g(x)=2tan(6x)(1cos2(6x))g'(x)=2\tan(6x)(\frac{1}{\cos^2(6x)})
  4. h(x)=5csc2(x)h'(x)=−5\csc^2(x)

🌟 Closing

Practice these rules, and you’ll soon find them as intuitive as the basic derivatives! Keep up the great work. 🌈

Key Terms to Review (10)

(-csc(x)cot(x))

: The term (-csc(x)cot(x)) represents the product of the cosecant and cotangent functions of an angle x, with a negative sign in front. It is commonly used in trigonometric identities and calculations.

(-csc^2(x))

: The term (-csc^2(x)) represents the derivative of the cosecant function squared. It measures how fast the cosecant function is changing at a specific point on its graph, multiplied by -1.

(cot(x))'

: The term (cot(x))' represents the derivative of the cotangent function. It measures how fast the cotangent function is changing at a specific point on its graph.

(sec^2(x))

: The term (sec^2(x)) represents the derivative of the secant function. It measures how fast the secant function is changing at a specific point on its graph.

Chain Rule

: The chain rule is a formula used to find the derivative of a composition of two or more functions. It states that the derivative of a composite function is equal to the derivative of the outermost function times the derivative of the innermost function.

Cotangent

: Cotangent is one of six trigonometric ratios used in right triangles. It represents the ratio between adjacent side length and opposite side length in relation to an acute angle.

Derivatives

: Derivatives are the rates at which quantities change. They measure how a function behaves as its input (x-value) changes.

sec(x)'

: The derivative of sec(x), which represents the rate of change of the secant function with respect to x.

Secant

: The secant of an angle in a right triangle is the ratio of the length of the hypotenuse to the length of the adjacent side.

Tangent

: A tangent line is a straight line that touches a curve at only one point and has the same slope as the curve at that point.


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© 2024 Fiveable Inc. All rights reserved.

AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.