These curves are circles which intersect at the origin and at ( 1 2 2 a , 4 ) . At the origin, the first
These curves are circles which intersect at the origin and at At the origin, the first circle has a horizontal tangent and the second a vertical one, so the tangents are perpendicular here. For the first circle asinacos asinasin at and acos at so the tangent here is vertical. Similarly, for the second circle and asin at so the tangent is horizontal, and again the tangents are perpendicular.
