Trigonometry Examples

Solve for θ in Degrees cos(theta)^2+2cos(theta)=0
Step 1
Factor the left side of the equation.
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Step 1.1
Let . Substitute for all occurrences of .
Step 1.2
Factor out of .
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Step 1.2.1
Factor out of .
Step 1.2.2
Factor out of .
Step 1.2.3
Factor out of .
Step 1.3
Replace all occurrences of with .
Step 2
If any individual factor on the left side of the equation is equal to , the entire expression will be equal to .
Step 3
Set equal to and solve for .
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Step 3.1
Set equal to .
Step 3.2
Solve for .
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Step 3.2.1
Take the inverse cosine of both sides of the equation to extract from inside the cosine.
Step 3.2.2
Simplify the right side.
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Step 3.2.2.1
The exact value of is .
Step 3.2.3
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 3.2.4
Subtract from .
Step 3.2.5
Find the period of .
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Step 3.2.5.1
The period of the function can be calculated using .
Step 3.2.5.2
Replace with in the formula for period.
Step 3.2.5.3
The absolute value is the distance between a number and zero. The distance between and is .
Step 3.2.5.4
Divide by .
Step 3.2.6
The period of the function is so values will repeat every degrees in both directions.
, for any integer
, for any integer
, for any integer
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
Subtract from both sides of the equation.
Step 4.2.2
The range of cosine is . Since does not fall in this range, there is no solution.
No solution
No solution
No solution
Step 5
The final solution is all the values that make true.
, for any integer
Step 6
Consolidate the answers.
, for any integer