Derivative Rules are a set of rules that need to be followed while differentiating different functions. Rules of Derivative are also called Differentiation Rules. Differentiation or derivatives is a method of finding the change in a value to some other value.
Derivative helps us find the instant rate of change of a quantity at a specific point. Some functions can be differentiated directly, but in certain cases, we use rules of derivatives to find the derivative of a function. These rules of derivatives help us to solve the problem easily and efficiently. In this article, we shall discuss the Rules of Derivatives in detail.
What are Rules of Derivatives?
We have learned to express the mathematical writing of differentiating a function f(x) with respect to x as:
f'(x) = d(f(x))/dx
where d/dx represent the differentiation and f'(x) is the function after differentiation.
In some conditions, the given function f(x) may not be a simple function but a special function or a compound function. In this case we need to use rules of derivatives to solve them. There are different rules of derivatives which are as follows:
Different Rules of Derivatives
We will study the following rules of derivative:
Power Rule of Derivative
Power rule of differentiation says that if the given function is of the form xn ,where n is any constant, then we can differentiate the function in the following way:
f(x) = xn
f'(x) = d((xn))/dx
f'(x) = nxn-1
This means that in such a case the differentiation is equal to the variable raised to 1 less than the original power and multiplied by the original power.
Let us understand it with an example.
Example: Differentiate the function f(x) = x3 with respect to x.
Given f(x) = x3
⇒ f'(x) = d/dx(x3)
⇒ f'(x) = 3x3-1
⇒ f'(x) = 3x2
Product Rule of Derivative
Product rule of differentiation states that if the function f(x) can be written as the product of two functions, g(x) and h(x), then the derivative of f(x) is found by:
f(x) = g(x).h(x)
f'(x) = g'(x)h(x) + g(x)h'(x)
Let us understand it with an example.
Example: Differentiate the function f(x) = (x+1)(x+2) with respect to x.
Given f(x) = (x+1)(x+2)
As the given function is a product of two functions g(x) = x+1 and h(x) = x+2, we can find the derivative of f(x) as:
f(x) = g(x).h(x)
⇒ f'(x) = g'(x)h(x) + g(x)h'(x)
⇒ f′(x) = (x+2).d/d​x(x+1) + (x+1).d/d​x(x+2)
⇒ f'(x) = (x+2) + (x+1)
⇒ f'(x) = 2x + 3
Quotient Rule of Derivative
Quotient rule of differentiation says that if the function f(x) can be written as the quotient of two functions, g(x) and h(x), then the derivative of f(x) is calculated as follows:
[Tex]f(x) = \frac{g(x)}{h(x)}\\
\Rightarrow f'(x) = \frac{g'(x)h(x) – g(x)h'(x)}{(h(x))^2}
[/Tex]
Let us understand it with an example.
Example: Differentiate the function [Tex]f(x) = \frac{(x+1)}{(x+2)}
[/Tex]with respect to x.
Given f(x) = (x+1)(x+2)
As the given function is a product of two functions g(x) = x+1 and h(x) = x+2, we can find the derivative of f(x) as:
[Tex]f(x) = \frac{g(x)}{h(x)}\\ \Rightarrow f'(x) = \frac{g'(x)h(x) – g(x)h'(x)}{(h(x))^2}\\ \Rightarrow f'(x) = \frac{(x+2).\frac{d}{dx}(x+1) – (x+1).\frac{d}{dx}(x+2)}{(x+2)^2}\\ \Rightarrow f'(x) = \frac{x+2 – (x+1) }{(x+2)^2}\\ \Rightarrow f'(x) = \frac{1}{(x+2)^2}
[/Tex]
Chain Rule of Derivative
Chain rule of differentiation states that if a function y = f(x) = g(t), where t = h(x), then differentiating f(x) can be done as follows:
f(x) = g(t)
⇒ f(x) = g(h(x))
⇒ f′(x) = d/d​x(g(h(x))
⇒ f'(x) = g'(h(x)).h'(x)
Let us understand it with an example.
Example: Differentiate the function f(x) = sin(x2) with respect to x.
Given f(x) = sin(x2)
We can consider g(t) = sin (t) and h(x) = x2
Thus f(x) = g(h(x))
Using chain rule,
f'(x) = g'(h(x)).h'(x), and
g'(t) = d/dt(sin t) = cos t
⇒ g'(x) = cos x
⇒ h'(t) = d/dt(t2) = 2t
⇒ h'(x) = 2x
⇒ f'(x) = cos(x2).2x = 2x.cos(x2)
Sum and Difference Rule of Derivative
If a function f(x) is the sum or difference of two functions, g(x) and h(x), then the derivative of f(x) is equal to the sum or difference of the derivatives of g(x) and h(x). Mathematically, it can be written as:
For a function f such that,
f(x) = g(x) ± h(x)
⇒ d/dx(f(x)) = d/dx{g(x) ± h(x)}
⇒ d/dx(f(x)) = d/dx{g(x)} ± d/dx{h(x)}
⇒ f'(x) = g'(x) ± h'(x)
Let us understand it with an example.
Example: Find the derivative of f(x) = sin(x) + cos(x) with respect to x.
Given f(x) = sin(x) + cos(x)
Let g(x) = sin(x) and h(x) = cos(x)
As f(x) = g(x) + h(x)
⇒ f'(x) = g'(x) + h'(x)
⇒ [Tex]f'(x) = \frac{d}{dx}(\sin x)+ \frac{d}{dx}(\cos x)
[/Tex]
⇒ f'(x) = cos x – sin x
Derivative Rules for Constant Multiple
This rule of differentiation says that if a function is multiplied by a constant, the constant remains the same during differentiation and can be taken out of the derivative. Thus, if we have a function f(x) and it is multiplied by any constant ‘a’, then
d/dx{a.f(x)} = a.d/dx{f(x)} = a.f'(x)
Let us understand it with an example.
Example: Calculate the derivative of f(x) = 3x3.
Solution:
f(x) = 3x3
⇒ f'(x) = d/dx(3x3)
⇒ f'(x) = 3.d/dx(x3)
⇒ f'(x) = 3(3x2) = 9x2
Derivative Rules for Various Functions
In this section, we will discuss the rules of differentiation for the below listed functions:
Derivative Rules for Trigonometric Function
Trigonometry makes use of 6 functions which are sin, cos, tan, sec, cosec and cot. The derivatives of these 6 functions is given below:
| f(x) | f'(x) |
|---|
| sin(x) | cos(x) |
| cos(x) | -sin(x) |
| tan(x) | sec2x |
| sec(x) | sec(x)tan(x) |
| cosec(x) | -cosec(x)cot(x) |
| cot(x) | -cosec2x |
Derivative Rules for Inverse Trigonometric Function
Trigonometry also has 6 inverse functions which are sin-1, cos-1, tan-1, sec-1, cosec-1, and cot-1. The derivatives of these 6 functions is given below:
| f(x) | f'(x) |
|---|
| sin-1(x) | 1/√(1-x2) |
| cos-1(x) | -1/√(1-x2) |
| tan-1(x) | 1/(1+x2) |
| sec-1(x) | 1/[x√(x2-1)] where x ≠-1, 0, 1 |
| cosec-1(x) | -1/[x√(x2-1)] where x ≠-1, 0, 1 |
| cot-1(x) | -1/(1+x2) |
Derivative Rules for Exponential Function
Any function which has ‘e’ is said to be an exponential function. Generally, we have two types of exponential functions which are given in the table below along with their derivatives:
Derivative Rules for Logarithmic Function
Any function which involves ‘e’ is said to be a Logarithmic function. Generally, we have two types of Logarithmic functions which are given in the table below along with their derivatives:
| f(x) | f'(x) |
|---|
| loga x | 1/(x ln(a)) or 1/(x loge a) |
| ln(x) or loge x | 1/x |
Derivative Rules for Hyperbolic Function
Each trigonometric function has a corresponding hyperbolic function which is named by adding an ‘h’ after the name of a trigonometric function. Thus we have 6 hyperbolic functions which are given below along with their derivatives:
| f(x) | f'(x) |
|---|
| sinh(x) | cosh(x) |
| cosh(x) | sinh(x) |
| tanh(x) | sech2(x) |
| sech(x) | -sech(x)tanh(x) |
| cosech(x) | -cosech(x)coth(x) |
| coth(x) | -cosech2(x) |
Derivative Rules for Inverse Hyperbolic Function
Each inverse trigonometric function has a corresponding inverse hyperbolic function which is named by adding an ‘h’ after the name of an inverse trigonometric function. Thus we have 6 inverse hyperbolic functions which are given below along with their derivatives:
| f(x) | f'(x) |
|---|
| sinh-1(x) | 1/√(1+x2) |
| cosh-1(x) | 1/√(x2-1) |
| tanh-1(x) | 1/(1-x2) |
| sech-1(x) | -1/√x(1-x2) |
| cosech-1(x) | -1/|x|√(1-x2) |
| coth-1(x) | 1/(1-x2) |
Derivative Rules for Composite Function
If a function f(x) is of the form g(h(x)) then,
f'(x) = g'(h(x)).h'(x)
This is the same as the chain rule. Refer to the example of the chain rule to understand it.
Derivative Rules for Parametric Function
If we have two functions x(t) and y(t) then we calculate dy/dx as follows:
- First, we calculate the derivative of x(t) with respect to t.
- Then we calculate the derivative of y(t) with respect to t.
- Divide the derivative of y(t) by x(t) to get dy/dx.
dy/dx = x'(t)/y'(t)
Let us understand it with an example.
Example: Calculate dy/dx if x(t) = sin(x) y(t) = x2.
x(t) = sin(x)
⇒ x'(t) = cos(x)
and y(t) = x2
⇒ y'(t) = 2x
Thus, dy/dx = 2x/cos(x) = 2x.sec(x)
Derivative Rules for Implicit Function
A function that comprises both dependent and independent variables is called an implicit function. In such cases, it may not be easy to change the function into an explicit function. For example, if we have a function in variables x and y, then it may not be possible to write the function as y = f(x). In such cases, we differentiate the function by separating the variables on two sides of the equality sign.
Consider a function x2 + y = 3. This function can be differentiated as follows:
Given: x2 + y = 3
Separating the variables on both sides of the equation, we get:
y = 3 – x2
Now differentiating both sides w.r.t x, we get:
dy/dx = 0 – 2x
dy/dx = -2x
Derivative Rules for Infinite Series
If we have a function [Tex]y = f(x) = x^{x^{x^{\ldots\infty}}}
[/Tex]then, derivative of f(x) is calculated as:
[Tex]y = f(x) = x^{x^{x^{\ldots\infty}}} \\ y = x^y\\
[/Tex]
Taking logarithm on both sides, we get:
log y = y.log x
Differentiating both sides with respect to x, we get:
[Tex]\frac{1}{y}\frac{dy}{dx} = \frac{dy}{dx}\log x+y\frac{d}{dx}(\log x)\\ \frac{1}{y}\frac{dy}{dx} = \frac{dy}{dx}\log x + \frac{y}{x}\\ \frac{dy}{dx}(\frac{1}{y}-\log x) = \frac{y}{x}\\ \frac{dy}{dx}\frac{(1-y\log x)}{y} = \frac{y}{x}\\ \frac{dy}{dx} = \frac{y^2}{x(1-y\log x)}
[/Tex]
Partial Derivative Rules
Partial Derivative is applicable to multivariable function in which the function is differentiated with respect to a particular variable and the other variables are treated as scalar multiple. Product, quotient, power and chain rule are applicable to the partial derivatives also in the same way as they are applicable to complete derivatives.
Consider two functions u = f(x, y) and v = g(x, y) to be functions of x and y. Then the rules of derivatives can be applied to it as follows:
Product Rule of Partial Derivative
If there is a function h(x, y) which is a product of u and v then:
[Tex]\frac{\partial h}{\partial x} = \frac{\partial f}{\partial x}.g(x, y)+f(x, y)\frac{\partial g}{\partial x}\\ \frac{\partial h}{\partial y} = \frac{\partial f}{\partial y}.g(x, y)+f(x, y)\frac{\partial g}{\partial y}
[/Tex]
Quotient Rule of Partial Derivative
If there is a function h(x, y) which is a division of u and v then:
[Tex]h(x, y) = \frac{f(x, y)}{g(x,y)}\\ \frac{\partial h}{\partial x} = \frac{\frac{\partial f}{\partial x}.g(x, y)-f(x, y)\frac{\partial g}{\partial x}}{(g(x,y))^2}\\ \frac{\partial h}{\partial y} = \frac{\frac{\partial f}{\partial y}.g(x, y)-f(x, y)\frac{\partial g}{\partial y}}{(g(x,y))^2}
[/Tex]
Power Rule of Partial Derivative
According to this rule, if h(x, y) is a power of any function f(x, y), then:
h(x, y) = [f(x,y)]n
[Tex]\frac{\partial h}{\partial x} = n[f(x,y)]^{n-1}.\frac{\partial f}{\partial x}\\ \frac{\partial h}{\partial y} = n[f(x,y)]^{n-1}.\frac{\partial f}{\partial y}
[/Tex]
Chain Rule of Partial Derivative
According to this rule, if u = f(x, y) and x = (s, t) and y = (s, t), then:
[Tex]\frac{\partial u}{\partial s} = \frac{\partial u}{\partial x}.\frac{\partial x}{\partial s}+\frac{\partial u}{\partial y}.\frac{\partial y}{\partial s}\\ \frac{\partial u}{\partial t} = \frac{\partial u}{\partial x}.\frac{\partial x}{\partial t}+\frac{\partial u}{\partial y}.\frac{\partial y}{\partial t}
[/Tex]
Also, Check
Solved Examples on Derivative Rules
Example 1. Find the derivative of f(x) = (x+2)(x-7).
Solution:
f(x) = (x+2) (x-7)
g(x) = x+2 and h(x) = x-7
Using product rule, we get
f'(x) = g'(x)h(x) + g(x)h'(x)
f'(x)= 1(x-7) + (x+2)(1)
f'(x) = x – 7 + x + 2
f'(x)= 2x -5
Example 2. Find the derivative of f(x) = sin(x)/x.
Solution:
f(x) = sin(x)/x
g(x) = sin(x) and h(x) = x
Using quotient rule,
[Tex]f(x) = \frac{g(x)}{h(x)}\\ f'(x) = \frac{g'(x)h(x) – g(x)h'(x)}{(h(x))^2}\\ f'(x) = \frac{x\frac{d}{dx}(\sin x)-\sin(x)\frac{d}{dx}(x)}{x^2}\\ f'(x) = \frac{x\cos x- sinx}{x^2}
[/Tex]
Example 3. Find the derivative of f(x) = sin(x).cos(x).
Solution:
f(x) = sin(x).cos(x)
g(x) = sin(x) and h(x) = cos(x)
Using product rule,
f'(x) = g'(x)h(x) + g(x)h'(x)
f'(x) = cos(x).cos(x) + sin(x)[-sin(x)]
f'(x) = cos2x – sin2x = cos(2x)
Example 4. Find the derivative of f(x) = sec(2x+3).
Solution:
Given f(x) = sec(2x+3)
g(t) = sec(t) and t = h(x) = 2x+3
Using chain rule,
g'(t) = sec(t)tan(t) or g(x) = sec(x)tan(x)
h'(x) = 2
f'(x) = g'(h(x)).h'(x)
f'(x) = sec(2x+3)tan(2x+2)*2 = 2sec(2x+3)tan(2x+3)
Example 5. Find the derivative of f(x) = x2 + x + 1.
Solution:
Given f(x) = x2 + x + 1
Using sum/ difference rule
f'(x) = d/dx(x2) + d/dx(x) + d/dx(1)
f'(x) = 2x + 1 + 0
Practice Problems on Derivative Rules
Problem 1. Find the derivative of (x2+4)/x+1.
Problem 2. Find the derivative of log(2x)/x.
Problem 3. Find the derivative of tan(sin(x)).
Problem 4. Find the derivative of 9x6 + 2x.
Problem 5. Find the derivative of sin(x) + 3x2 + log(x).cos(x).
FAQs on Derivative Rules
What are 7 Rules of Derivatives?
Various rules of derivatives are:
- Product rule
- Chain rule
- Quotient rule
- Sum Rule
- Difference rule
- Constant Multiple Rule
- Power rule
What do you mean by Differentiation?
Differentiation is the method used to find the change in a quantity with respect to another quantity.
Why do we use Differentiation Rules?
We use rules of derivatives to calculate the derivative when we are given compound or composite functions which cannot be differentiated directly.
State Product Rule of Derivatives.
According to product rule of derivatives:
If a given function f(x) can be expressed as a product of two functions, g(x) and h(x) then the derivative of f(x) is calculated as follows:
f(x) = g(x).h(x)
f'(x) = g'(x)h(x) + g(x)h'(x)
State Power Rule of Derivatives?
According to power rule, if a given function is of the form xn, where n is any constant, then we can differentiate the function in the following way:
f(x) = xn
f'(x) = d((xn))/dx
f'(x) = nx{n-1}
Can more than One Rule be used in a Single Derivative?
Yes we can make use of more than one rule of derivative in a single derivative. For example when f(x) = sin(x2), we need to use chain rule as well as power rule.
What are Four Basic Derivative Rules?
Four basic derivative rules are,
- Power Rule
- Sum/Difference Rule
- Product/Quotient Rule
- Chain Rule
What are Derivative Rules of e?
Derivative rule of e is, d/dx(e) = 0
What are Differentiation Rules Trig?
Some differentiation rule for trigonometric functions are,
- Derivation of sin x: (sin x)’ = cos x
- Derivative of cos x: (cos x)’ = -sin x
- Derivative of tan x: (tan x)’ = sec2 x
- Derivative of cot x: (cot x)’ = -cosec2 x
What are Applications of Derivative Rules?
Applications of Derivatives are,
- Rate of Change of a Quantity
- Approximation or Finding Approximate Value
- Equation of a Tangent and Normal To a Curve
- Maxima and Minima
- Point of Inflection
What are ln Derivative Rules?
ln derivative rule is “Derivative of ln x is 1/x”. It is mathematically written as: d/dx (ln x) = 1/x
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