Derivatives - Product Rule for Derivatives
Introduction
The product rule is a formula used to find the derivative of a function that is the product of two other functions.
If we have two functions, f(x) and g(x), then the product rule states:
(f * g)' = f' * g + f * g'
Explanation
- The derivative of the product of two functions is equal to the derivative of the first function times the second function plus the first function times the derivative of the second function.
Example 1
Find the derivative of the function f(x) = x^2 * sin(x)
.
Step 1: Identify f(x) and g(x).
- f(x) = x^2
- g(x) = sin(x)
Step 2: Find f’(x) and g’(x).
- f’(x) = 2x
- g’(x) = cos(x)
Step 3: Apply the product rule formula.
(f * g)' = f' * g + f * g'
(x^2 * sin(x))' = (2x * sin(x)) + (x^2 * cos(x))
Example 2
Find the derivative of the function f(x) = e^x * ln(x)
.
Step 1: Identify f(x) and g(x).
- f(x) = e^x
- g(x) = ln(x)
Step 2: Find f’(x) and g’(x).
- f’(x) = e^x
- g’(x) = 1/x
Step 3: Apply the product rule formula.
(f * g)' = f' * g + f * g'
(e^x * ln(x))' = (e^x * 1/x) + (e^x * ln(x))
Derivative Rules Reminder
- The power rule:
(x^n)' = nx^(n-1)
- The constant rule:
(c)' = 0
- The sum rule:
(f + g)' = f' + g'
Conclusion
The product rule allows us to find the derivative of a function that is the product of two other functions. By using the formula (f * g)' = f' * g + f * g'
, we can differentiate such functions efficiently and accurately.
Derivatives of Trigonometric Functions
Derivative of sin(x)
- The derivative of
sin(x)
is cos(x)
.
- Example:
(sin(x))' = cos(x)
Derivative of cos(x)
- The derivative of
cos(x)
is -sin(x)
.
- Example:
(cos(x))' = -sin(x)
Derivative of tan(x)
- The derivative of
tan(x)
is sec^2(x)
.
- Example:
(tan(x))' = sec^2(x)
Derivative of csc(x)
- The derivative of
csc(x)
is -csc(x) * cot(x)
.
- Example:
(csc(x))' = -csc(x) * cot(x)
Derivative of sec(x)
- The derivative of
sec(x)
is sec(x) * tan(x)
.
- Example:
(sec(x))' = sec(x) * tan(x)
Chain Rule for Derivatives
- The chain rule allows us to find the derivative of composite functions.
- If
f(g(x))
is a composite function, then its derivative is given by f'(g(x)) * g'(x)
.
Example 1
Find the derivative of the function f(x) = sin(2x)
.
Step 1: Identify f(x) and g(x).
- f(x) = sin(x)
- g(x) = 2x
Step 2: Find f’(x) and g’(x).
- f’(x) = cos(x)
- g’(x) = 2
Step 3: Apply the chain rule formula.
(f(g(x)))' = f'(g(x)) * g'(x)
(sin(2x))' = cos(2x) * 2
Example 2
Find the derivative of the function f(x) = e^(3x)
.
Step 1: Identify f(x) and g(x).
- f(x) = e^x
- g(x) = 3x
Step 2: Find f’(x) and g’(x).
- f’(x) = e^x
- g’(x) = 3
Step 3: Apply the chain rule formula.
(f(g(x)))' = f'(g(x)) * g'(x)
(e^(3x))' = e^(3x) * 3
Chain Rule with Multiple Functions
- The chain rule can be applied to functions with multiple nested functions.
- Example:
f(g(h(x)))
- The derivative would be
f'(g(h(x))) * g'(h(x)) * h'(x)
Conclusion
- Understanding the derivatives of trigonometric functions and the chain rule is important for solving complex problems in calculus.
- The derivative rules and formulas discussed in these slides can be applied to a wide range of mathematical functions and help in finding rates of change and optimizing functions.
- Regular practice and problem-solving can further enhance your understanding and proficiency in applying these concepts.
Slide 21
- Applications of Integration
- Area under a curve
- Volume of revolution
- Finding the center of mass
- Determining arc length
- Solving differential equations
Slide 22
- Area under a curve
- Integrating a function gives the area between the curve and the x-axis.
Example: Find the area under the curve
y = sin(x)
from x = 0
to x = π
.
Slide 23
- Volume of revolution
- Integrating a function multiplied by its radius squared gives the volume of the solid formed by rotating the curve about an axis.
Example: Find the volume of the solid formed by rotating the curve
y = x^2
about the x-axis from x = 0
to x = 2
.
Slide 24
- Finding the center of mass
- Integrating a function multiplied by its distance from an axis gives the weighted average position of the mass.
Example: Find the x-coordinate of the center of mass of the region bounded by the curve
y = x^2
and the x-axis.
Slide 25
- Determining arc length
- Integrating the square root of the sum of the squares of the derivatives gives the length of a curve.
Example: Find the length of the curve
y = e^x
from x = 0
to x = 1
.
Slide 26
- Solving differential equations
- Integration plays a crucial role in solving differential equations, which model various processes in science and engineering.
Example: Solve the differential equation
y' = 2x
with the initial condition y(0) = 1
.
Slide 27
- Integration by Parts
- Another technique to evaluate integrals is integration by parts.
- It is based on the product rule of differentiation.
Formula: ∫ u dv = u v - ∫ v du
Slide 28
- Example: Evaluating an integral using integration by parts
∫ x ln(x) dx
Step 1: Choose u and dv
u = ln(x) dv = x dx
Slide 29
- Example: Evaluating an integral using integration by parts
Step 2: Find du and v
du = (1/x) dx v = x^2/2
Step 3: Apply the integration by parts formula
∫ x ln(x) dx = (x^2/2) ln(x) - ∫ (x^2/2) (1/x) dx
Slide 30
- Example: Evaluating an integral using integration by parts
Step 4: Simplify the right-hand side
∫ x ln(x) dx = (x^2/2) ln(x) - ∫ (x/2) dx
= (x^2/2) ln(x) - (x^2/4) + C
where C is the constant of integration.