-- Mathlib/Analysis/Convex/Combination.lean
theorem Convex.centerMass_mem (hs : Convex R s) :
    (∀ i ∈ t, 0 ≤ w i) → (0 < ∑ i ∈ t, w i) → (∀ i ∈ t, z i ∈ s) → t.centerMass w z ∈ s

Proof state:
case neg
R : Type u_1
E : Type u_3
ι : Type u_5
inst✝² : LinearOrderedField R
inst✝¹ : AddCommGroup E
inst✝ : Module R E
s : Set E
t✝ : Finset ι
w : ι → R
z : ι → E
hs : Convex R s
i : ι
t : Finset ι
hi : i ∉ t
ht : (∀ i ∈ t, 0 ≤ w i) → 0 < ∑ i ∈ t, w i → (∀ i ∈ t, z i ∈ s) → t.centerMass w z ∈ s
h₀ : ∀ i_1 ∈ insert i t, 0 ≤ w i_1
hpos : 0 < w i + ∑ x ∈ t, w x
hmem : ∀ i_1 ∈ insert i t, z i_1 ∈ s
zi : z i ∈ s
hs₀ : ∀ j ∈ t, 0 ≤ w j
hsum_t : ¬∑ j ∈ t, w j = 0
⊢ (w i / (w i + ∑ j ∈ t, w j)) • z i + ((∑ j ∈ t, w j) / (w i + ∑ j ∈ t, w j)) • t.centerMass w z ∈ s

Tactic:
refine convex_iff_div.1 hs zi (ht hs₀ ?_ ?_) ?_ (sum_nonneg hs₀) hpos

Result:
case neg.refine_1
R : Type u_1
E : Type u_3
ι : Type u_5
inst✝² : LinearOrderedField R
inst✝¹ : AddCommGroup E
inst✝ : Module R E
s : Set E
t✝ : Finset ι
w : ι → R
z : ι → E
hs : Convex R s
i : ι
t : Finset ι
hi : i ∉ t
ht : (∀ i ∈ t, 0 ≤ w i) → 0 < ∑ i ∈ t, w i → (∀ i ∈ t, z i ∈ s) → t.centerMass w z ∈ s
h₀ : ∀ i_1 ∈ insert i t, 0 ≤ w i_1
hpos : 0 < w i + ∑ x ∈ t, w x
hmem : ∀ i_1 ∈ insert i t, z i_1 ∈ s
zi : z i ∈ s
hs₀ : ∀ j ∈ t, 0 ≤ w j
hsum_t : ¬∑ j ∈ t, w j = 0
⊢ 0 < ∑ i ∈ t, w i

case neg.refine_2
R : Type u_1
E : Type u_3
ι : Type u_5
inst✝² : LinearOrderedField R
inst✝¹ : AddCommGroup E
inst✝ : Module R E
s : Set E
t✝ : Finset ι
w : ι → R
z : ι → E
hs : Convex R s
i : ι
t : Finset ι
hi : i ∉ t
ht : (∀ i ∈ t, 0 ≤ w i) → 0 < ∑ i ∈ t, w i → (∀ i ∈ t, z i ∈ s) → t.centerMass w z ∈ s
h₀ : ∀ i_1 ∈ insert i t, 0 ≤ w i_1
hpos : 0 < w i + ∑ x ∈ t, w x
hmem : ∀ i_1 ∈ insert i t, z i_1 ∈ s
zi : z i ∈ s
hs₀ : ∀ j ∈ t, 0 ≤ w j
hsum_t : ¬∑ j ∈ t, w j = 0
⊢ ∀ i ∈ t, z i ∈ s

case neg.refine_3
R : Type u_1
E : Type u_3
ι : Type u_5
inst✝² : LinearOrderedField R
inst✝¹ : AddCommGroup E
inst✝ : Module R E
s : Set E
t✝ : Finset ι
w : ι → R
z : ι → E
hs : Convex R s
i : ι
t : Finset ι
hi : i ∉ t
ht : (∀ i ∈ t, 0 ≤ w i) → 0 < ∑ i ∈ t, w i → (∀ i ∈ t, z i ∈ s) → t.centerMass w z ∈ s
h₀ : ∀ i_1 ∈ insert i t, 0 ≤ w i_1
hpos : 0 < w i + ∑ x ∈ t, w x
hmem : ∀ i_1 ∈ insert i t, z i_1 ∈ s
zi : z i ∈ s
hs₀ : ∀ j ∈ t, 0 ≤ w j
hsum_t : ¬∑ j ∈ t, w j = 0
⊢ 0 ≤ w i

Proof state:
case pos
R : Type u_1
E : Type u_3
ι : Type u_5
inst✝² : LinearOrderedField R
inst✝¹ : AddCommGroup E
inst✝ : Module R E
s : Set E
t✝ : Finset ι
w : ι → R
z : ι → E
hs : Convex R s
i : ι
t : Finset ι
hi : i ∉ t
ht : (∀ i ∈ t, 0 ≤ w i) → 0 < ∑ i ∈ t, w i → (∀ i ∈ t, z i ∈ s) → t.centerMass w z ∈ s
h₀ : ∀ i_1 ∈ insert i t, 0 ≤ w i_1
hpos : 0 < w i + ∑ x ∈ t, w x
hmem : ∀ i_1 ∈ insert i t, z i_1 ∈ s
zi : z i ∈ s
hs₀ : ∀ j ∈ t, 0 ≤ w j
hsum_t : ∑ j ∈ t, w j = 0
ws : ∀ j ∈ t, w j = 0
wz : ∑ j ∈ t, w j • z j = 0
⊢ (w i)⁻¹ • w i • z i ∈ s

Tactic:
simp only [hsum_t, add_zero] at hpos

Result:
case pos
R : Type u_1
E : Type u_3
ι : Type u_5
inst✝² : LinearOrderedField R
inst✝¹ : AddCommGroup E
inst✝ : Module R E
s : Set E
t✝ : Finset ι
w : ι → R
z : ι → E
hs : Convex R s
i : ι
t : Finset ι
hi : i ∉ t
ht : (∀ i ∈ t, 0 ≤ w i) → 0 < ∑ i ∈ t, w i → (∀ i ∈ t, z i ∈ s) → t.centerMass w z ∈ s
h₀ : ∀ i_1 ∈ insert i t, 0 ≤ w i_1
hmem : ∀ i_1 ∈ insert i t, z i_1 ∈ s
zi : z i ∈ s
hs₀ : ∀ j ∈ t, 0 ≤ w j
hsum_t : ∑ j ∈ t, w j = 0
ws : ∀ j ∈ t, w j = 0
wz : ∑ j ∈ t, w j • z j = 0
hpos : 0 < w i
⊢ (w i)⁻¹ • w i • z i ∈ s

Proof state:
case insert
R : Type u_1
E : Type u_3
ι : Type u_5
inst✝² : LinearOrderedField R
inst✝¹ : AddCommGroup E
inst✝ : Module R E
s : Set E
t✝ : Finset ι
w : ι → R
z : ι → E
hs : Convex R s
i : ι
t : Finset ι
hi : i ∉ t
ht : (∀ i ∈ t, 0 ≤ w i) → 0 < ∑ i ∈ t, w i → (∀ i ∈ t, z i ∈ s) → t.centerMass w z ∈ s
⊢ (∀ i_1 ∈ insert i t, 0 ≤ w i_1) →
    0 < ∑ i ∈ insert i t, w i → (∀ i_1 ∈ insert i t, z i_1 ∈ s) → (insert i t).centerMass w z ∈ s

Tactic:
intro h₀ hpos hmem

Result:
case insert
R : Type u_1
E : Type u_3
ι : Type u_5
inst✝² : LinearOrderedField R
inst✝¹ : AddCommGroup E
inst✝ : Module R E
s : Set E
t✝ : Finset ι
w : ι → R
z : ι → E
hs : Convex R s
i : ι
t : Finset ι
hi : i ∉ t
ht : (∀ i ∈ t, 0 ≤ w i) → 0 < ∑ i ∈ t, w i → (∀ i ∈ t, z i ∈ s) → t.centerMass w z ∈ s
h₀ : ∀ i_1 ∈ insert i t, 0 ≤ w i_1
hpos : 0 < ∑ i ∈ insert i t, w i
hmem : ∀ i_1 ∈ insert i t, z i_1 ∈ s
⊢ (insert i t).centerMass w z ∈ s

Proof state:
case neg.refine_2
R : Type u_1
E : Type u_3
ι : Type u_5
inst✝² : LinearOrderedField R
inst✝¹ : AddCommGroup E
inst✝ : Module R E
s : Set E
t✝ : Finset ι
w : ι → R
z : ι → E
hs : Convex R s
i : ι
t : Finset ι
hi : i ∉ t
ht : (∀ i ∈ t, 0 ≤ w i) → 0 < ∑ i ∈ t, w i → (∀ i ∈ t, z i ∈ s) → t.centerMass w z ∈ s
h₀ : ∀ i_1 ∈ insert i t, 0 ≤ w i_1
hpos : 0 < w i + ∑ x ∈ t, w x
hmem : ∀ i_1 ∈ insert i t, z i_1 ∈ s
zi : z i ∈ s
hs₀ : ∀ j ∈ t, 0 ≤ w j
hsum_t : ¬∑ j ∈ t, w j = 0
j : ι
hj : j ∈ t
⊢ z j ∈ s

Tactic:
exact hmem j (mem_insert_of_mem hj)

Result:
no goals

Proof state:
case pos
R : Type u_1
E : Type u_3
ι : Type u_5
inst✝² : LinearOrderedField R
inst✝¹ : AddCommGroup E
inst✝ : Module R E
s : Set E
t✝ : Finset ι
w : ι → R
z : ι → E
hs : Convex R s
i : ι
t : Finset ι
hi : i ∉ t
ht : (∀ i ∈ t, 0 ≤ w i) → 0 < ∑ i ∈ t, w i → (∀ i ∈ t, z i ∈ s) → t.centerMass w z ∈ s
h₀ : ∀ i_1 ∈ insert i t, 0 ≤ w i_1
hmem : ∀ i_1 ∈ insert i t, z i_1 ∈ s
zi : z i ∈ s
hs₀ : ∀ j ∈ t, 0 ≤ w j
hsum_t : ∑ j ∈ t, w j = 0
ws : ∀ j ∈ t, w j = 0
wz : ∑ j ∈ t, w j • z j = 0
hpos : 0 < w i
⊢ z i ∈ s

Tactic:
exact zi

Result:
no goals

Proof state:
case pos
R : Type u_1
E : Type u_3
ι : Type u_5
inst✝² : LinearOrderedField R
inst✝¹ : AddCommGroup E
inst✝ : Module R E
s : Set E
t✝ : Finset ι
w : ι → R
z : ι → E
hs : Convex R s
i : ι
t : Finset ι
hi : i ∉ t
ht : (∀ i ∈ t, 0 ≤ w i) → 0 < ∑ i ∈ t, w i → (∀ i ∈ t, z i ∈ s) → t.centerMass w z ∈ s
h₀ : ∀ i_1 ∈ insert i t, 0 ≤ w i_1
hpos : 0 < w i + ∑ x ∈ t, w x
hmem : ∀ i_1 ∈ insert i t, z i_1 ∈ s
zi : z i ∈ s
hs₀ : ∀ j ∈ t, 0 ≤ w j
hsum_t : ∑ j ∈ t, w j = 0
ws : ∀ j ∈ t, w j = 0
wz : ∑ j ∈ t, w j • z j = 0
⊢ (insert i t).centerMass w z ∈ s

Tactic:
simp only [centerMass, sum_insert hi, wz, hsum_t, add_zero]

Result:
case pos
R : Type u_1
E : Type u_3
ι : Type u_5
inst✝² : LinearOrderedField R
inst✝¹ : AddCommGroup E
inst✝ : Module R E
s : Set E
t✝ : Finset ι
w : ι → R
z : ι → E
hs : Convex R s
i : ι
t : Finset ι
hi : i ∉ t
ht : (∀ i ∈ t, 0 ≤ w i) → 0 < ∑ i ∈ t, w i → (∀ i ∈ t, z i ∈ s) → t.centerMass w z ∈ s
h₀ : ∀ i_1 ∈ insert i t, 0 ≤ w i_1
hpos : 0 < w i + ∑ x ∈ t, w x
hmem : ∀ i_1 ∈ insert i t, z i_1 ∈ s
zi : z i ∈ s
hs₀ : ∀ j ∈ t, 0 ≤ w j
hsum_t : ∑ j ∈ t, w j = 0
ws : ∀ j ∈ t, w j = 0
wz : ∑ j ∈ t, w j • z j = 0
⊢ (w i)⁻¹ • w i • z i ∈ s

Proof state:
case empty
R : Type u_1
E : Type u_3
ι : Type u_5
inst✝² : LinearOrderedField R
inst✝¹ : AddCommGroup E
inst✝ : Module R E
s : Set E
t : Finset ι
w : ι → R
z : ι → E
hs : Convex R s
⊢ (∀ i ∈ ∅, 0 ≤ w i) → 0 < ∑ i ∈ ∅, w i → (∀ i ∈ ∅, z i ∈ s) → ∅.centerMass w z ∈ s

Tactic:
simp [lt_irrefl]

Result:
no goals