Problem 98 of 7
Find all angles in interval [0,2pi) with cosine value -sqrt(2)/2.
Hints
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use unit-circle symmetry.
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Use unit-circle symmetry for exact common cosine values.
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Correct
Your answer is equivalent to the expected form.
Solution
Walkthrough
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1. Find the reference angle for the cosine magnitude.
2. Use cosine sign to choose quadrants.
3. List every angle in the interval.
Use the worked steps, then substitute the final answer back into the original relationship to confirm it satisfies the prompt.
Sine-symmetry quadrants for a cosine prompt.