Copy of An equiangular spiral - parametric equation
An equiangular spiral, also known as a logarithmic spiral is a curve with the property that the angle  between the tangent and the radius at any point of the spiral is constant.
In polar coordinates:  where  and  are positive real constants. 
In parametric form:  , where  and  are real constants.
Move the point  over the spiral to see the constant angle  between the radius and the tangent.
Consider .