Equation Icon  { ( t ) } 𝒜 = Exp [th ] = e −0t |t ∈ ℝ ≃ ℝ, (6.14 ) 0 e { ( cos(t) sin (t)) } 𝒦 = Exp [tτ y] = |t ∈ [0,2π [ ≃ ℝ ∕ℤ. (6.15 ) − sin(t) cos(t)