Algebra-2

Question Analysis
This question involves evaluating the parent sine function at a key x-value ( ). The main focus is on recalling the output of at the midpoint of one full cycle, with no transformations.

Key Concept Explanation
The parent sine function has 5 "key points" that mark critical stages of its cycle: start ( ), peak ( ), midpoint ( ), trough ( ), and end ( ). At , the function returns to the x-axis (midline), so its y-value is a known, fixed number.

Step-by-step Solution
1. Recognize as a key point of : It is the midpoint of one full cycle (between and ).
2. Recall the value of : For the parent function, .
Alternative verification with unit circle: At angle (180°), the unit circle point is ; since

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