What side length can make a triangle with side lengths of 6 and 6?

I am not sure what you are asking but I will give you as much information about this triangle as I can and you can ask me whatever you want to about it.

Equilateral triangle. Sides: a = 6 b = 6 c = 6

Area: T = 15.588

Perimeter: p = 18

Semiperimeter: s = 9

Angle ∠ A = α = 60° = 1.047 rad

Angle ∠ B = β = 60° = 1.047 rad

Angle ∠ C = γ = 60° = 1.047 rad

Height: ha = 5.19 6

Height: hb = 5.19 6

Height: hc = 5.19 6

Median: ma = 5.19 6

Median: mb = 5.19 6

Median: mc = 5.19 6

Inradius: r = 1.732

Circumradius: R = 3.464

Vertex coordinates: A[6; 0] B[0; 0] C[3; 5.196]

Centroid: CG[3; 1.732]

Coordinates of the circumcenter: U[3; 1.732 ]