#[Visualizing the graph of the sine function][Visualización de la gráfica de la función seno]#

The circle shown on the right has a radius of one unit.

Each point on the circle gives an angle made with the positive $x$axis if you connect that point to the origin.

The angles, in radians, of points on the circle are calibrated around the circle as shown.

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

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.