Merge branch 'LagrangeDerivative' into ChebyshevExtremal

Author: YuvalFilmus

Mathlib/Data/Finset/Powerset.lean

@@ -74,16 +74,16 @@ theorem powerset_eq_singleton_empty : s.powerset = {∅} ↔ s = ∅ := by
   rw [← powerset_empty, powerset_inj]
 
 theorem image_injOn_powerset_of_injOn {β : Type*} [DecidableEq β] {f : α → β} (H : Set.InjOn f s) :
-    Set.InjOn (fun (x : Finset α) => x.image f) s.powerset := by
+    Set.InjOn (α := Finset α) (·.image f) s.powerset := by
   have {z a} (_ : z ⊆ s) (_ : a ∈ s) : a ∈ z ↔ f a ∈ z.image f := by grind [H.eq_iff]
   exact fun _ _ _ _ _ => by grind
 
 theorem image_surjOn_powerset {β : Type*} [DecidableEq β] {f : α → β} :
-    Set.SurjOn (fun (x : Finset α) => x.image f) s.powerset (s.image f).powerset :=
+    Set.SurjOn (α := Finset α) (·.image f) s.powerset (s.image f).powerset :=
   fun t ht => ⟨{ x ∈ s | f x ∈ t}, by grind⟩
 
 theorem powerset_image {β : Type*} [DecidableEq β] {f : α → β} :
-    (s.image f).powerset = s.powerset.image (fun x => x.image f) :=
+    (s.image f).powerset = s.powerset.image (·.image f) :=
   ext fun a => ⟨fun _ => mem_image.mpr ⟨{ x ∈ s | f x ∈ a}, by grind⟩, by grind⟩
 
 /-- **Number of Subsets of a Set** -/