case inl
θ ψ : ℝ
Hcos : cos θ = cos ψ
Hsin : sin θ = sin ψ
hc : ↑θ = ↑ψ
⊢ ↑θ = ↑ψ

case inr
θ ψ : ℝ
Hcos : cos θ = cos ψ
Hsin : sin θ = sin ψ
hc : ↑θ = -↑ψ
⊢ ↑θ = ↑ψ
θ ψ : ℝ
Hcos : cos θ = cos ψ
Hsin : sin θ = sin ψ
⊢ ↑θ = ↑ψ
cases' cos_eq_iff_coe_eq_or_eq_neg.mp Hcos with hc hc
case inr.inl
θ ψ : ℝ
Hcos : cos θ = cos ψ
Hsin : sin θ = sin ψ
hc : ↑θ = -↑ψ
hs : ↑θ = ↑ψ
⊢ ↑θ = ↑ψ

case inr.inr
θ ψ : ℝ
Hcos : cos θ = cos ψ
Hsin : sin θ = sin ψ
hc : ↑θ = -↑ψ
hs : ↑θ + ↑ψ = ↑π
⊢ ↑θ = ↑ψ
case inr
θ ψ : ℝ
Hcos : cos θ = cos ψ
Hsin : sin θ = sin ψ
hc : ↑θ = -↑ψ
⊢ ↑θ = ↑ψ
cases' sin_eq_iff_coe_eq_or_add_eq_pi.mp Hsin with hs hs
case inr.inr
θ ψ : ℝ
Hcos : cos θ = cos ψ
Hsin : sin θ = sin ψ
hc : ↑π = 0
hs : ↑θ + ↑ψ = ↑π
⊢ ↑θ = ↑ψ
case inr.inr
θ ψ : ℝ
Hcos : cos θ = cos ψ
Hsin : sin θ = sin ψ
hc : ↑θ = -↑ψ
hs : ↑θ + ↑ψ = ↑π
⊢ ↑θ = ↑ψ
rw [eq_neg_iff_add_eq_zero, hs] at hc
case inr.inr.intro
θ ψ : ℝ
Hcos : cos θ = cos ψ
Hsin : sin θ = sin ψ
hc : ↑π = 0
hs : ↑θ + ↑ψ = ↑π
n : ℤ
hn : n • (2 * π) = -π + 0
⊢ ↑θ = ↑ψ
case inr.inr
θ ψ : ℝ
Hcos : cos θ = cos ψ
Hsin : sin θ = sin ψ
hc : ↑π = 0
hs : ↑θ + ↑ψ = ↑π
⊢ ↑θ = ↑ψ
obtain ⟨n, hn⟩ : ∃ n, n • _ = _ := QuotientAddGroup.leftRel_apply.mp (Quotient.exact' hc)
case inr.inr.intro
θ ψ : ℝ
Hcos : cos θ = cos ψ
Hsin : sin θ = sin ψ
hc : ↑π = 0
hs : ↑θ + ↑ψ = ↑π
n : ℤ
hn✝ : n • (2 * π) = -1 * π
hn : n * 2 + 1 = 0
⊢ ↑θ = ↑ψ
case inr.inr.intro
θ ψ : ℝ
Hcos : cos θ = cos ψ
Hsin : sin θ = sin ψ
hc : ↑π = 0
hs : ↑θ + ↑ψ = ↑π
n : ℤ
hn : n • (2 * π) = -π + 0
⊢ ↑θ = ↑ψ
rw [← neg_one_mul, add_zero, ← sub_eq_zero, zsmul_eq_mul, ← mul_assoc, ← sub_mul, mul_eq_zero,
  eq_false (ne_of_gt pi_pos), or_false_iff, sub_neg_eq_add, ← Int.cast_zero, ← Int.cast_one,
  ← Int.int_cast_ofNat,  ← Int.cast_mul, ← Int.cast_add, Int.cast_inj] at hn
case inr.inr.intro
θ ψ : ℝ
Hcos : cos θ = cos ψ
Hsin : sin θ = sin ψ
hc : ↑π = 0
hs : ↑θ + ↑ψ = ↑π
n : ℤ
hn✝ : n • (2 * π) = -1 * π
hn : n * 2 + 1 = 0
this : 1 % 2 = 0 % 2
⊢ ↑θ = ↑ψ
case inr.inr.intro
θ ψ : ℝ
Hcos : cos θ = cos ψ
Hsin : sin θ = sin ψ
hc : ↑π = 0
hs : ↑θ + ↑ψ = ↑π
n : ℤ
hn✝ : n • (2 * π) = -1 * π
hn : n * 2 + 1 = 0
this : (n * 2 + 1) % 2 = 0 % 2
⊢ ↑θ = ↑ψ
rw [add_comm, Int.add_mul_emod_self] at this
no goals
case inr.inr.intro
θ ψ : ℝ
Hcos : cos θ = cos ψ
Hsin : sin θ = sin ψ
hc : ↑π = 0
hs : ↑θ + ↑ψ = ↑π
n : ℤ
hn✝ : n • (2 * π) = -1 * π
hn : n * 2 + 1 = 0
this : 1 % 2 = 0 % 2
⊢ ↑θ = ↑ψ
exact absurd this one_ne_zero
no goals
case inl
θ ψ : ℝ
Hcos : cos θ = cos ψ
Hsin : sin θ = sin ψ
hc : ↑θ = ↑ψ
⊢ ↑θ = ↑ψ
exact hc
no goals
case inr.inl
θ ψ : ℝ
Hcos : cos θ = cos ψ
Hsin : sin θ = sin ψ
hc : ↑θ = -↑ψ
hs : ↑θ = ↑ψ
⊢ ↑θ = ↑ψ
exact hs