Calculus Examples

Find the Critical Points sin(x)-cos(x)
Step 1
Find the first derivative.
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Step 1.1
Find the first derivative.
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Step 1.1.1
By the Sum Rule, the derivative of with respect to is .
Step 1.1.2
The derivative of with respect to is .
Step 1.1.3
Evaluate .
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Step 1.1.3.1
Since is constant with respect to , the derivative of with respect to is .
Step 1.1.3.2
The derivative of with respect to is .
Step 1.1.3.3
Multiply by .
Step 1.1.3.4
Multiply by .
Step 1.2
The first derivative of with respect to is .
Step 2
Set the first derivative equal to then solve the equation .
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Step 2.1
Set the first derivative equal to .
Step 2.2
Divide each term in the equation by .
Step 2.3
Cancel the common factor of .
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Step 2.3.1
Cancel the common factor.
Step 2.3.2
Rewrite the expression.
Step 2.4
Convert from to .
Step 2.5
Separate fractions.
Step 2.6
Convert from to .
Step 2.7
Divide by .
Step 2.8
Multiply by .
Step 2.9
Subtract from both sides of the equation.
Step 2.10
Take the inverse tangent of both sides of the equation to extract from inside the tangent.
Step 2.11
Simplify the right side.
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Step 2.11.1
The exact value of is .
Step 2.12
The tangent function is negative in the second and fourth quadrants. To find the second solution, subtract the reference angle from to find the solution in the third quadrant.
Step 2.13
Simplify the expression to find the second solution.
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Step 2.13.1
Add to .
Step 2.13.2
The resulting angle of is positive and coterminal with .
Step 2.14
Find the period of .
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Step 2.14.1
The period of the function can be calculated using .
Step 2.14.2
Replace with in the formula for period.
Step 2.14.3
The absolute value is the distance between a number and zero. The distance between and is .
Step 2.14.4
Divide by .
Step 2.15
Add to every negative angle to get positive angles.
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Step 2.15.1
Add to to find the positive angle.
Step 2.15.2
To write as a fraction with a common denominator, multiply by .
Step 2.15.3
Combine fractions.
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Step 2.15.3.1
Combine and .
Step 2.15.3.2
Combine the numerators over the common denominator.
Step 2.15.4
Simplify the numerator.
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Step 2.15.4.1
Move to the left of .
Step 2.15.4.2
Subtract from .
Step 2.15.5
List the new angles.
Step 2.16
The period of the function is so values will repeat every radians in both directions.
, for any integer
, for any integer
Step 3
Find the values where the derivative is undefined.
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Step 3.1
The domain of the expression is all real numbers except where the expression is undefined. In this case, there is no real number that makes the expression undefined.
Step 4
Evaluate at each value where the derivative is or undefined.
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Step 4.1
Evaluate at .
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Step 4.1.1
Substitute for .
Step 4.1.2
Simplify.
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Step 4.1.2.1
Simplify each term.
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Step 4.1.2.1.1
Apply the reference angle by finding the angle with equivalent trig values in the first quadrant.
Step 4.1.2.1.2
The exact value of is .
Step 4.1.2.1.3
Apply the reference angle by finding the angle with equivalent trig values in the first quadrant. Make the expression negative because cosine is negative in the second quadrant.
Step 4.1.2.1.4
The exact value of is .
Step 4.1.2.1.5
Multiply .
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Step 4.1.2.1.5.1
Multiply by .
Step 4.1.2.1.5.2
Multiply by .
Step 4.1.2.2
Simplify terms.
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Step 4.1.2.2.1
Combine the numerators over the common denominator.
Step 4.1.2.2.2
Add and .
Step 4.1.2.2.3
Cancel the common factor of .
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Step 4.1.2.2.3.1
Cancel the common factor.
Step 4.1.2.2.3.2
Divide by .
Step 4.2
Evaluate at .
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Step 4.2.1
Substitute for .
Step 4.2.2
Simplify.
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Step 4.2.2.1
Simplify each term.
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Step 4.2.2.1.1
Apply the reference angle by finding the angle with equivalent trig values in the first quadrant. Make the expression negative because sine is negative in the fourth quadrant.
Step 4.2.2.1.2
The exact value of is .
Step 4.2.2.1.3
Apply the reference angle by finding the angle with equivalent trig values in the first quadrant.
Step 4.2.2.1.4
The exact value of is .
Step 4.2.2.2
Simplify terms.
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Step 4.2.2.2.1
Combine the numerators over the common denominator.
Step 4.2.2.2.2
Subtract from .
Step 4.2.2.2.3
Cancel the common factor of and .
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Step 4.2.2.2.3.1
Factor out of .
Step 4.2.2.2.3.2
Cancel the common factors.
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Step 4.2.2.2.3.2.1
Factor out of .
Step 4.2.2.2.3.2.2
Cancel the common factor.
Step 4.2.2.2.3.2.3
Rewrite the expression.
Step 4.2.2.2.3.2.4
Divide by .
Step 4.3
List all of the points.
, for any integer
, for any integer
Step 5