An equiangular spiral, also known as a logarithmic spiral is a curve with the property that the angle [math]α[/math] between the tangent and the radius at any point of the spiral is constant.[br]In polar coordinates: [math]r=ae^{bθ}[/math] where [math]a[/math] and [math]b[/math] are positive real constants. [br][br]In parametric form: [math]x(t)=ae^{bt} cos(t); y(t)=ae^{bt} sin(t)[/math] where [math]a[/math] and [math]b[/math] are real numbers. [br][br][list][br][*]Move the point [math]R[/math] over the spiral to see the constant angle [math]α[/math] between the radius and the tangent.[br][*]Consider a>0; a<0; [br] [*] α>90°, α<90°, α=90°.[br][/list]