English
If i and j belong to s, then the sum of affineCombinationLineMapWeights over t ∈ s equals 1: ∑_{t∈s} affineCombinationLineMapWeights i j c t = 1.
Русский
Если i и j принадлежат s, то сумма весов affineCombinationLineMapWeights по t ∈ s равна 1: ∑_{t∈s} affineCombinationLineMapWeights i j c t = 1.
LaTeX
$$$\sum_{t \in s} \operatorname{affineCombinationLineMapWeights}(k,i,j,c,t) = 1$$$
Lean4
@[simp]
theorem sum_affineCombinationLineMapWeights [DecidableEq ι] {i j : ι} (hi : i ∈ s) (hj : j ∈ s) (c : k) :
∑ t ∈ s, affineCombinationLineMapWeights i j c t = 1 :=
by
simp_rw [affineCombinationLineMapWeights, Pi.add_apply, sum_add_distrib]
simp [hi, hj, ← mul_sum]