Calculus Examples

Find the Local Maxima and Minima f(x)=x+sin(x)
Step 1
Find the first derivative of the function.
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Step 1.1
Differentiate.
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Step 1.1.1
By the Sum Rule, the derivative of with respect to is .
Step 1.1.2
Differentiate using the Power Rule which states that is where .
Step 1.2
The derivative of with respect to is .
Step 2
Find the second derivative of the function.
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Step 2.1
Differentiate.
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Step 2.1.1
By the Sum Rule, the derivative of with respect to is .
Step 2.1.2
Since is constant with respect to , the derivative of with respect to is .
Step 2.2
The derivative of with respect to is .
Step 2.3
Subtract from .
Step 3
To find the local maximum and minimum values of the function, set the derivative equal to and solve.
Step 4
Subtract from both sides of the equation.
Step 5
Take the inverse cosine of both sides of the equation to extract from inside the cosine.
Step 6
Simplify the right side.
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Step 6.1
The exact value of is .
Step 7
The cosine function is negative in the second and third quadrants. To find the second solution, subtract the reference angle from to find the solution in the third quadrant.
Step 8
Subtract from .
Step 9
The solution to the equation .
Step 10
Evaluate the second derivative at . If the second derivative is positive, then this is a local minimum. If it is negative, then this is a local maximum.
Step 11
Evaluate the second derivative.
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Step 11.1
Apply the reference angle by finding the angle with equivalent trig values in the first quadrant.
Step 11.2
The exact value of is .
Step 11.3
Multiply by .
Step 12
Since there is at least one point with or undefined second derivative, apply the first derivative test.
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Step 12.1
Split into separate intervals around the values that make the first derivative or undefined.
Step 12.2
Substitute any number, such as , from the interval in the first derivative to check if the result is negative or positive.
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Step 12.2.1
Replace the variable with in the expression.
Step 12.2.2
Simplify the result.
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Step 12.2.2.1
The exact value of is .
Step 12.2.2.2
Add and .
Step 12.2.2.3
The final answer is .
Step 12.3
Substitute any number, such as , from the interval in the first derivative to check if the result is negative or positive.
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Step 12.3.1
Replace the variable with in the expression.
Step 12.3.2
Simplify the result.
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Step 12.3.2.1
Evaluate .
Step 12.3.2.2
Add and .
Step 12.3.2.3
The final answer is .
Step 12.4
Since the first derivative did not change signs around , this is not a local maximum or minimum.
Not a local maximum or minimum
Step 12.5
No local maxima or minima found for .
No local maxima or minima
No local maxima or minima
Step 13