Real.sin_mul_sum_cos

∀ (n : ℕ) (a b : ℝ),
  Real.sin (a / 2) * ∑ i ∈ Finset.range n, Real.cos (a * ↑i + b) =
    Real.sin (↑n * a / 2) * Real.cos ((↑n - 1) * a / 2 + b)

Defined in: Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex
Cited by: 0 results in Mathlib
Foundations: Depth 152 from the axioms · uses propext, Classical.choice, Quot.sound

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