The sine function, \( \sin \theta \), is negative in the third and fourth quadrants of the unit circle.
Let's analyze the given angles:
- \( \sin(120^\circ) \): This angle is in the second quadrant, where sine is positive.
- \( \sin(270^\circ) \): This angle is on the negative y-axis, where sine is negative.
- \( \sin(0^\circ) \): This angle is at the origin (positive x-axis), where sine is zero.
- \( \sin(90^\circ) \): This angle is on the positive y-axis, where sine is positive.
Based on this analysis, the only angle where \( \sin \theta \) is negative is:
\( \sin(270^\circ) \).