mathlib3 documentation

ring_theory.power_series.well_known

Definition of well-known power series #

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In this file we define the following power series:

def power_series.inv_units_sub {R : Type u_1} [ring R] (u : Rˣ) :

The power series for 1 / (u - x).

Equations
@[simp]
theorem power_series.coeff_inv_units_sub {R : Type u_1} [ring R] (u : Rˣ) (n : ) :
def power_series.exp (A : Type u_1) [ring A] [algebra A] :

Power series for the exponential function at zero.

Equations
def power_series.sin (A : Type u_1) [ring A] [algebra A] :

Power series for the sine function at zero.

Equations
def power_series.cos (A : Type u_1) [ring A] [algebra A] :

Power series for the cosine function at zero.

Equations
@[simp]
@[simp]
theorem power_series.coeff_sin_bit0 {A : Type u_1} [ring A] [algebra A] (n : ) :
@[simp]
theorem power_series.coeff_cos_bit1 {A : Type u_1} [ring A] [algebra A] (n : ) :
@[simp]
theorem power_series.map_exp {A : Type u_1} {A' : Type u_2} [ring A] [ring A'] [algebra A] [algebra A'] (f : A →+* A') :
@[simp]
theorem power_series.map_sin {A : Type u_1} {A' : Type u_2} [ring A] [ring A'] [algebra A] [algebra A'] (f : A →+* A') :
@[simp]
theorem power_series.map_cos {A : Type u_1} {A' : Type u_2} [ring A] [ring A'] [algebra A] [algebra A'] (f : A →+* A') :

Shows that $e^{aX} * e^{bX} = e^{(a + b)X}$

Shows that $(e^{X})^k = e^{kX}$.

theorem power_series.exp_pow_sum {A : Type u_1} [comm_ring A] [algebra A] (n : ) :
(finset.range n).sum (λ (k : ), power_series.exp A ^ k) = power_series.mk (λ (p : ), (finset.range n).sum (λ (k : ), k ^ p * (algebra_map A) ((p.factorial))⁻¹))

Shows that $\sum_{k = 0}^{n - 1} (e^{X})^k = \sum_{p = 0}^{\infty} \sum_{k = 0}^{n - 1} \frac{k^p}{p!}X^p$.