Basic concept: Because the radius of polar coordinates here is a positive number according to the standard, it represents the length in geometry (the length is always a positive number). A is a parameter, which specifies a radius greater than zero (indicating the starting position θ=0).

The circle formed by the curve ρ=2acosθ is on the right side of the polar axis, that is, it starts from the region of (-π/2, π/2).