English
If f and g are circle-integrable on the same circle, then the circle integral of f − g equals the difference of the circle integrals of f and g.
Русский
Если f и g кругово интегрируемы на одной окружности, то интеграл f−g равен разности интегралов от f и g.
LaTeX
$$$CircleIntegrable f c R \\to CircleIntegrable g c R \\Rightarrow \\oint z in C(c,R), (f(z) - g(z)) \\,dz = \\oint z in C(c,R), f(z) \\,dz - \\oint z in C(c,R), g(z) \\,dz$$$
Lean4
theorem integral_sub {f g : ℂ → E} {c : ℂ} {R : ℝ} (hf : CircleIntegrable f c R) (hg : CircleIntegrable g c R) :
(∮ z in C(c, R), f z - g z) = (∮ z in C(c, R), f z) - ∮ z in C(c, R), g z := by
simp only [circleIntegral, smul_sub, intervalIntegral.integral_sub hf.out hg.out]