Trigonometry Examples

Find the x and y Intercepts f(x)=5cos(3x)-5
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
Divide by .
Step 1.2.4
Take the inverse cosine of both sides of the equation to extract from inside the cosine.
Step 1.2.5
Simplify the right side.
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Step 1.2.5.1
The exact value of is .
Step 1.2.6
Divide each term in by and simplify.
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Step 1.2.6.1
Divide each term in by .
Step 1.2.6.2
Simplify the left side.
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Step 1.2.6.2.1
Cancel the common factor of .
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Step 1.2.6.2.1.1
Cancel the common factor.
Step 1.2.6.2.1.2
Divide by .
Step 1.2.6.3
Simplify the right side.
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Step 1.2.6.3.1
Divide by .
Step 1.2.7
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
Solve for .
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Step 1.2.8.1
Simplify.
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Step 1.2.8.1.1
Multiply by .
Step 1.2.8.1.2
Add and .
Step 1.2.8.2
Divide each term in by and simplify.
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Step 1.2.8.2.1
Divide each term in by .
Step 1.2.8.2.2
Simplify the left side.
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Step 1.2.8.2.2.1
Cancel the common factor of .
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Step 1.2.8.2.2.1.1
Cancel the common factor.
Step 1.2.8.2.2.1.2
Divide by .
Step 1.2.9
Find the period of .
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Step 1.2.9.1
The period of the function can be calculated using .
Step 1.2.9.2
Replace with in the formula for period.
Step 1.2.9.3
The absolute value is the distance between a number and zero. The distance between and is .
Step 1.2.10
The period of the function is so values will repeat every radians in both directions.
, 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
Multiply by .
Step 2.2.2.1.2
The exact value of is .
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