Trigonometry Examples

Solve for x in Radians sin(2x)+cos(x)=0
Step 1
Apply the sine double-angle identity.
Step 2
Factor out of .
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Step 2.1
Factor out of .
Step 2.2
Raise to the power of .
Step 2.3
Factor out of .
Step 2.4
Factor out of .
Step 3
If any individual factor on the left side of the equation is equal to , the entire expression will be equal to .
Step 4
Set equal to and solve for .
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Step 4.1
Set equal to .
Step 4.2
Solve for .
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Step 4.2.1
Take the inverse cosine of both sides of the equation to extract from inside the cosine.
Step 4.2.2
Simplify the right side.
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Step 4.2.2.1
The exact value of is .
Step 4.2.3
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 4.2.4
Simplify .
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Step 4.2.4.1
To write as a fraction with a common denominator, multiply by .
Step 4.2.4.2
Combine fractions.
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Step 4.2.4.2.1
Combine and .
Step 4.2.4.2.2
Combine the numerators over the common denominator.
Step 4.2.4.3
Simplify the numerator.
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Step 4.2.4.3.1
Multiply by .
Step 4.2.4.3.2
Subtract from .
Step 4.2.5
Find the period of .
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Step 4.2.5.1
The period of the function can be calculated using .
Step 4.2.5.2
Replace with in the formula for period.
Step 4.2.5.3
The absolute value is the distance between a number and zero. The distance between and is .
Step 4.2.5.4
Divide by .
Step 4.2.6
The period of the function is so values will repeat every radians in both directions.
, for any integer
, for any integer
, for any integer
Step 5
Set equal to and solve for .
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Step 5.1
Set equal to .
Step 5.2
Solve for .
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Step 5.2.1
Subtract from both sides of the equation.
Step 5.2.2
Divide each term in by and simplify.
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Step 5.2.2.1
Divide each term in by .
Step 5.2.2.2
Simplify the left side.
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Step 5.2.2.2.1
Cancel the common factor of .
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Step 5.2.2.2.1.1
Cancel the common factor.
Step 5.2.2.2.1.2
Divide by .
Step 5.2.2.3
Simplify the right side.
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Step 5.2.2.3.1
Move the negative in front of the fraction.
Step 5.2.3
Take the inverse sine of both sides of the equation to extract from inside the sine.
Step 5.2.4
Simplify the right side.
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Step 5.2.4.1
The exact value of is .
Step 5.2.5
The sine function is negative in the third and fourth quadrants. To find the second solution, subtract the solution from , to find a reference angle. Next, add this reference angle to to find the solution in the third quadrant.
Step 5.2.6
Simplify the expression to find the second solution.
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Step 5.2.6.1
Subtract from .
Step 5.2.6.2
The resulting angle of is positive, less than , and coterminal with .
Step 5.2.7
Find the period of .
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Step 5.2.7.1
The period of the function can be calculated using .
Step 5.2.7.2
Replace with in the formula for period.
Step 5.2.7.3
The absolute value is the distance between a number and zero. The distance between and is .
Step 5.2.7.4
Divide by .
Step 5.2.8
Add to every negative angle to get positive angles.
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Step 5.2.8.1
Add to to find the positive angle.
Step 5.2.8.2
To write as a fraction with a common denominator, multiply by .
Step 5.2.8.3
Combine fractions.
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Step 5.2.8.3.1
Combine and .
Step 5.2.8.3.2
Combine the numerators over the common denominator.
Step 5.2.8.4
Simplify the numerator.
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Step 5.2.8.4.1
Multiply by .
Step 5.2.8.4.2
Subtract from .
Step 5.2.8.5
List the new angles.
Step 5.2.9
The period of the function is so values will repeat every radians in both directions.
, for any integer
, for any integer
, for any integer
Step 6
The final solution is all the values that make true.
, for any integer
Step 7
Consolidate and to .
, for any integer