The vertical distance from the x-axis to the point. On a unit circle (r=1), it corresponds exactly to the y-coordinate.
y = sin(θ)
The horizontal distance from the origin to the point's vertical projection. It corresponds to the x-coordinate.
x = cos(θ)
The length of the segment on the tangent line (at x=1). It represents the slope of the radius.
tan(θ) = sin/cos
The reciprocal of tangent. Visually, it's the segment on the horizontal tangent line (at y=1).
cot(θ) = 1/tan
The reciprocal of cosine. It is the hypotenuse of the triangle formed by the tangent line and the x-axis.
sec(θ) = 1/cos
The reciprocal of sine. It is the hypotenuse of the triangle formed by the cotangent line and the y-axis.
csc(θ) = 1/sin