#[Visualizing the graph of the sine function][Visualización de la gráfica de la función seno]#
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The circle shown on the right has a radius of one unit.
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Each point on the circle gives an angle made with the positive $x$-axis if you connect that point to the origin.
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The angles, in radians, of points on the circle are calibrated around the circle as shown.
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The sine of an angle is the $y$-coordinate (height above the $x$-axis) of the corresponding point on the circle: $\sin \theta = y$-coordinate of dot on the circle
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As the circle rotates (or, equivalently, the point moves around the circle) so that the angle increases, the height of the dot traces out the sine curve.