English
The integral over θ of circleTransform equals a scaled circle integral with shifted center: ∫ circleTransform dθ = (2πi)^{-1} ∮ (z-w)^{-1} f(z) dz.
Русский
Интеграл по θ от circleTransform равен нормированному константному множителю контурному интегралу с центр смещён на w.
LaTeX
$$$$ \\int_{0}^{2\\pi} \\text{circleTransform}(f)(\\theta)\\, d\\theta = (2\\pi i)^{-1} \\oint_{|z-c|=R} (z-w)^{-1} f(z) \\,dz. $$$$
Lean4
theorem circleTransformDeriv_eq (f : ℂ → E) :
circleTransformDeriv R z w f = fun θ => (circleMap z R θ - w)⁻¹ • circleTransform R z w f θ :=
by
ext
simp_rw [circleTransformDeriv, circleTransform, ← mul_smul, ← mul_assoc]
ring_nf
rw [inv_pow]
congr
ring