The slider labelled "angle" controls the angle of the radius of the circle corresponding to point P on the circle.
The red point plots the x-coordinate of point P as a function of its angle - in other words, the red point plots the cosine of the angle.
The blue point plots the y-coordinate of the point P as a function of its angle - in other words, the blue point plots the sine of the angle.
The green point plots y-coordinate / x-coordinate - in other words, the tangent of the angle of P.
Move the dot labelled "angle" to change the angle corresponding to point P, and thereby to plot the cosine, sine, and tangent curves. (You can also use the arrow keys to move the dot on the slider after clicking on it.)

Observe what happens to the plots of the red, blue, and green points when the radius of the circle is increased.