Exponential, trigonometric and hyperbolic trigonometric functions #
This file contains the definitions of the real and complex exponential, sine, cosine, tangent, hyperbolic sine, hyperbolic cosine, and hyperbolic tangent functions.
The Cauchy sequence consisting of partial sums of the Taylor series of the complex exponential function
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The complex exponential function, defined via its Taylor series
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- Complex.exp z = CauSeq.lim (Complex.exp' z)
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The complex sine function, defined via exp
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- Complex.sin z = (Complex.exp (-z * Complex.I) - Complex.exp (z * Complex.I)) * Complex.I / 2
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The complex cosine function, defined via exp
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- Complex.cos z = (Complex.exp (z * Complex.I) + Complex.exp (-z * Complex.I)) / 2
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The complex tangent function, defined as sin z / cos z
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- Complex.tan z = Complex.sin z / Complex.cos z
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The complex hyperbolic sine function, defined via exp
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- Complex.sinh z = (Complex.exp z - Complex.exp (-z)) / 2
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The complex hyperbolic cosine function, defined via exp
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- Complex.cosh z = (Complex.exp z + Complex.exp (-z)) / 2
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The complex hyperbolic tangent function, defined as sinh z / cosh z
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- Complex.tanh z = Complex.sinh z / Complex.cosh z
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scoped notation for the complex exponential function
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- Complex.termCexp = Lean.ParserDescr.node `Complex.termCexp 1024 (Lean.ParserDescr.symbol "cexp")
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scoped notation for the real exponential function
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- Real.termRexp = Lean.ParserDescr.node `Real.termRexp 1024 (Lean.ParserDescr.symbol "rexp")
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the exponential function as a monoid hom from Multiplicative ℂ
to ℂ
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De Moivre's formula
the exponential function as a monoid hom from Multiplicative ℝ
to ℝ
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A finite initial segment of the exponential series, followed by an arbitrary tail.
For fixed n
this is just a linear map wrt r
, and each map is a simple linear function
of the previous (see expNear_succ
), with expNear n x r ⟶ exp x
as n ⟶ ∞
,
for any r
.
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- Real.expNear n x r = (Finset.sum (Finset.range n) fun (m : ℕ) => x ^ m / ↑(Nat.factorial m)) + x ^ n / ↑(Nat.factorial n) * r
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Extension for the positivity
tactic: Real.exp
is always positive.
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Extension for the positivity
tactic: Real.cosh
is always positive.