How many solutions does have in the interval ?
Answer and explanation
Correct answer: A.
- Step 1: Two angles have the same cosine when they are equal or negatives of each other (up to multiples of ): or .
- Step 2: The first gives : . The second gives : .
- Step 3: Combining and removing repeats, the solutions are , which is values.
Answer
.
Why not the others: counts only from the first family; drops one of the end points; and count repeated values twice.
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