Trigonometry Examples

Find the x and y Intercepts f(x)=8cos(x)^2-4
Step 1
Find the x-intercepts.
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Step 1.1
To find the x-intercept(s), substitute in for and solve for .
Step 1.2
Solve the equation.
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Step 1.2.1
Rewrite the equation as .
Step 1.2.2
Add to both sides of the equation.
Step 1.2.3
Divide each term in by and simplify.
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Step 1.2.3.1
Divide each term in by .
Step 1.2.3.2
Simplify the left side.
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Step 1.2.3.2.1
Cancel the common factor of .
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Step 1.2.3.2.1.1
Cancel the common factor.
Step 1.2.3.2.1.2
Divide by .
Step 1.2.3.3
Simplify the right side.
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Step 1.2.3.3.1
Cancel the common factor of and .
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Step 1.2.3.3.1.1
Factor out of .
Step 1.2.3.3.1.2
Cancel the common factors.
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Step 1.2.3.3.1.2.1
Factor out of .
Step 1.2.3.3.1.2.2
Cancel the common factor.
Step 1.2.3.3.1.2.3
Rewrite the expression.
Step 1.2.4
Take the specified root of both sides of the equation to eliminate the exponent on the left side.
Step 1.2.5
Simplify .
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Step 1.2.5.1
Rewrite as .
Step 1.2.5.2
Any root of is .
Step 1.2.5.3
Multiply by .
Step 1.2.5.4
Combine and simplify the denominator.
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Step 1.2.5.4.1
Multiply by .
Step 1.2.5.4.2
Raise to the power of .
Step 1.2.5.4.3
Raise to the power of .
Step 1.2.5.4.4
Use the power rule to combine exponents.
Step 1.2.5.4.5
Add and .
Step 1.2.5.4.6
Rewrite as .
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Step 1.2.5.4.6.1
Use to rewrite as .
Step 1.2.5.4.6.2
Apply the power rule and multiply exponents, .
Step 1.2.5.4.6.3
Combine and .
Step 1.2.5.4.6.4
Cancel the common factor of .
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Step 1.2.5.4.6.4.1
Cancel the common factor.
Step 1.2.5.4.6.4.2
Rewrite the expression.
Step 1.2.5.4.6.5
Evaluate the exponent.
Step 1.2.6
The complete solution is the result of both the positive and negative portions of the solution.
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Step 1.2.6.1
First, use the positive value of the to find the first solution.
Step 1.2.6.2
Next, use the negative value of the to find the second solution.
Step 1.2.6.3
The complete solution is the result of both the positive and negative portions of the solution.
Step 1.2.7
Set up each of the solutions to solve for .
Step 1.2.8
Solve for in .
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Step 1.2.8.1
Take the inverse cosine of both sides of the equation to extract from inside the cosine.
Step 1.2.8.2
Simplify the right side.
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Step 1.2.8.2.1
The exact value of is .
Step 1.2.8.3
The cosine function is positive in the first and fourth quadrants. To find the second solution, subtract the reference angle from to find the solution in the fourth quadrant.
Step 1.2.8.4
Simplify .
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Step 1.2.8.4.1
To write as a fraction with a common denominator, multiply by .
Step 1.2.8.4.2
Combine fractions.
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Step 1.2.8.4.2.1
Combine and .
Step 1.2.8.4.2.2
Combine the numerators over the common denominator.
Step 1.2.8.4.3
Simplify the numerator.
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Step 1.2.8.4.3.1
Multiply by .
Step 1.2.8.4.3.2
Subtract from .
Step 1.2.8.5
Find the period of .
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Step 1.2.8.5.1
The period of the function can be calculated using .
Step 1.2.8.5.2
Replace with in the formula for period.
Step 1.2.8.5.3
The absolute value is the distance between a number and zero. The distance between and is .
Step 1.2.8.5.4
Divide by .
Step 1.2.8.6
The period of the function is so values will repeat every radians in both directions.
, for any integer
, for any integer
Step 1.2.9
Solve for in .
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Step 1.2.9.1
Take the inverse cosine of both sides of the equation to extract from inside the cosine.
Step 1.2.9.2
Simplify the right side.
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Step 1.2.9.2.1
The exact value of is .
Step 1.2.9.3
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 1.2.9.4
Simplify .
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Step 1.2.9.4.1
To write as a fraction with a common denominator, multiply by .
Step 1.2.9.4.2
Combine fractions.
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Step 1.2.9.4.2.1
Combine and .
Step 1.2.9.4.2.2
Combine the numerators over the common denominator.
Step 1.2.9.4.3
Simplify the numerator.
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Step 1.2.9.4.3.1
Multiply by .
Step 1.2.9.4.3.2
Subtract from .
Step 1.2.9.5
Find the period of .
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Step 1.2.9.5.1
The period of the function can be calculated using .
Step 1.2.9.5.2
Replace with in the formula for period.
Step 1.2.9.5.3
The absolute value is the distance between a number and zero. The distance between and is .
Step 1.2.9.5.4
Divide by .
Step 1.2.9.6
The period of the function is so values will repeat every radians in both directions.
, for any integer
, for any integer
Step 1.2.10
List all of the solutions.
, for any integer
Step 1.2.11
Consolidate the answers.
, for any integer
, for any integer
Step 1.3
x-intercept(s) in point form.
x-intercept(s): , for any integer
x-intercept(s): , for any integer
Step 2
Find the y-intercepts.
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Step 2.1
To find the y-intercept(s), substitute in for and solve for .
Step 2.2
Solve the equation.
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Step 2.2.1
Remove parentheses.
Step 2.2.2
Simplify .
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Step 2.2.2.1
Simplify each term.
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Step 2.2.2.1.1
The exact value of is .
Step 2.2.2.1.2
One to any power is one.
Step 2.2.2.1.3
Multiply by .
Step 2.2.2.2
Subtract from .
Step 2.3
y-intercept(s) in point form.
y-intercept(s):
y-intercept(s):
Step 3
List the intersections.
x-intercept(s): , for any integer
y-intercept(s):
Step 4