Trigonometric functions #
Main definitions #
This file contains the following definitions:
- π, arcsin, arccos, arctan
- argument of a complex number
- logarithm on complex numbers
Main statements #
Many basic inequalities on trigonometric functions are established.
The continuity and differentiability of the usual trigonometric functions are proved, and their derivatives are computed.
polynomial.chebyshev.T_complex_cos: then-th Chebyshev polynomial evaluates oncomplex.cos θto the valuen * complex.cos θ.
Tags #
log, sin, cos, tan, arcsin, arccos, arctan, angle, argument
The complex sine function is everywhere strictly differentiable, with the derivative cos x.
The complex sine function is everywhere differentiable, with the derivative cos x.
The complex cosine function is everywhere strictly differentiable, with the derivative
-sin x.
The complex cosine function is everywhere differentiable, with the derivative -sin x.
The complex hyperbolic sine function is everywhere strictly differentiable, with the derivative
cosh x.
The complex hyperbolic sine function is everywhere differentiable, with the derivative
cosh x.
The complex hyperbolic cosine function is everywhere strictly differentiable, with the
derivative sinh x.
The complex hyperbolic cosine function is everywhere differentiable, with the derivative
sinh x.
Simp lemmas for derivatives of λ x, complex.cos (f x) etc., f : ℂ → ℂ #
Simp lemmas for derivatives of λ x, complex.cos (f x) etc., f : E → ℂ #
The number π = 3.14159265... Defined here using choice as twice a zero of cos in [1,2], from
which one can derive all its properties. For explicit bounds on π, see data.real.pi.
Equations
the series sqrt_two_add_series x n is sqrt(2 + sqrt(2 + ... )) with n square roots,
starting with x. We define it here because cos (pi / 2 ^ (n+1)) = sqrt_two_add_series 0 n / 2
Equations
- real.sqrt_two_add_series x (n + 1) = real.sqrt (2 + real.sqrt_two_add_series x n)
- real.sqrt_two_add_series x 0 = x
The type of angles
Equations
Equations
- real.angle.inhabited = {default := 0}
Equations
Inverse of the sin function, returns values in the range -π / 2 ≤ arcsin x ≤ π / 2.
It defaults to -π / 2 on (-∞, -1) and to π / 2 to (1, ∞).
Equations
- real.arcsin = coe ∘ set.Icc_extend real.arcsin._proof_1 ⇑(real.sin_order_iso.symm)
real.sin as a local_homeomorph between (-π / 2, π / 2) and (-1, 1).
Equations
- real.sin_local_homeomorph = {to_local_equiv := {to_fun := real.sin, inv_fun := real.arcsin, source := set.Ioo (-(π / 2)) (π / 2), target := set.Ioo (-1) 1, map_source' := real.maps_to_sin_Ioo, map_target' := real.sin_local_homeomorph._proof_1, left_inv' := real.sin_local_homeomorph._proof_2, right_inv' := real.sin_local_homeomorph._proof_3}, open_source := real.sin_local_homeomorph._proof_4, open_target := real.sin_local_homeomorph._proof_5, continuous_to_fun := real.sin_local_homeomorph._proof_6, continuous_inv_fun := real.sin_local_homeomorph._proof_7}
Inverse of the cos function, returns values in the range 0 ≤ arccos x and arccos x ≤ π.
If the argument is not between -1 and 1 it defaults to π / 2
Equations
- real.arccos x = π / 2 - real.arcsin x
arg returns values in the range (-π, π], such that for x ≠ 0,
sin (arg x) = x.im / x.abs and cos (arg x) = x.re / x.abs,
arg 0 defaults to 0
Equations
- x.arg = ite (0 ≤ x.re) (real.arcsin (x.im / complex.abs x)) (ite (0 ≤ x.im) (real.arcsin ((-x).im / complex.abs x) + π) (real.arcsin ((-x).im / complex.abs x) - π))
Inverse of the exp function. Returns values such that (log x).im > - π and (log x).im ≤ π.
log 0 = 0
Equations
- complex.log x = ↑(real.log (complex.abs x)) + (↑(x.arg)) * complex.I
complex.exp as a local_homeomorph with source = {z | -π < im z < π} and
target = {z | 0 < re z} ∪ {z | im z ≠ 0}. This definition is used to prove that complex.log
is complex differentiable at all points but the negative real semi-axis.
Equations
- complex.exp_local_homeomorph = local_homeomorph.of_continuous_open {to_fun := complex.exp, inv_fun := complex.log, source := {z : ℂ | z.im ∈ set.Ioo (-π) π}, target := {z : ℂ | 0 < z.re} ∪ {z : ℂ | z.im ≠ 0}, map_source' := complex.exp_local_homeomorph._proof_1, map_target' := complex.exp_local_homeomorph._proof_2, left_inv' := complex.exp_local_homeomorph._proof_3, right_inv' := complex.exp_local_homeomorph._proof_4} complex.exp_local_homeomorph._proof_5 complex.is_open_map_exp complex.exp_local_homeomorph._proof_6
The n-th Chebyshev polynomial of the first kind evaluates on cos θ to the
value cos (n * θ).
cos (n * θ) is equal to the n-th Chebyshev polynomial of the first kind evaluated
on cos θ.
The n-th Chebyshev polynomial of the second kind evaluates on cos θ to the
value sin ((n+1) * θ) / sin θ.
sin ((n + 1) * θ) is equal to sin θ multiplied with the n-th Chebyshev polynomial of the
second kind evaluated on cos θ.
real.tan as an order_iso between (-(π / 2), π / 2) and ℝ.
Equations
- real.tan_order_iso = (strict_mono_incr_on.order_iso real.tan (set.Ioo (-(π / 2)) (π / 2)) real.strict_mono_incr_on_tan).trans ((order_iso.set_congr (real.tan '' set.Ioo (-(π / 2)) (π / 2)) set.univ real.image_tan_Ioo).trans order_iso.set.univ)
Inverse of the tan function, returns values in the range -π / 2 < arctan x and
arctan x < π / 2
Equations
- real.arctan x = ↑(⇑(real.tan_order_iso.symm) x)
real.tan as a local_homeomorph between (-(π / 2), π / 2) and the whole line.
Equations
- real.tan_local_homeomorph = {to_local_equiv := {to_fun := real.tan, inv_fun := real.arctan, source := set.Ioo (-(π / 2)) (π / 2), target := set.univ ℝ, map_source' := real.tan_local_homeomorph._proof_1, map_target' := real.tan_local_homeomorph._proof_2, left_inv' := real.tan_local_homeomorph._proof_3, right_inv' := real.tan_local_homeomorph._proof_4}, open_source := real.tan_local_homeomorph._proof_5, open_target := real.tan_local_homeomorph._proof_6, continuous_to_fun := real.continuous_on_tan_Ioo, continuous_inv_fun := real.tan_local_homeomorph._proof_7}
Lemmas for derivatives of the composition of real.arctan with a differentiable function #
In this section we register lemmas for the derivatives of the composition of real.arctan with a
differentiable function, for standalone use and use with simp.