diff --git a/Mathlib/Analysis/Calculus/FDeriv/Symmetric.lean b/Mathlib/Analysis/Calculus/FDeriv/Symmetric.lean
index d6edcf594441c2..6c9bc82e3c4eb0 100644
--- a/Mathlib/Analysis/Calculus/FDeriv/Symmetric.lean
+++ b/Mathlib/Analysis/Calculus/FDeriv/Symmetric.lean
@@ -139,10 +139,10 @@ theorem Convex.taylor_approx_two_segment {v w : E} (hv : x + v ∈ interior s)
     calc
       ‖g' t‖ = ‖(f' (x + h • v + (t * h) • w) - f' x - f'' (h • v + (t * h) • w)) (h • w)‖ := by
         rw [hg']
-        have : h * (t * h) = t * (h * h) := by ring
-        simp only [ContinuousLinearMap.coe_sub', ContinuousLinearMap.map_add, pow_two,
-          ContinuousLinearMap.add_apply, Pi.smul_apply, smul_sub, smul_add, smul_smul, ← sub_sub,
-          ContinuousLinearMap.coe_smul', Pi.sub_apply, ContinuousLinearMap.map_smul, this]
+        congrm ‖?_‖
+        simp only [ContinuousLinearMap.sub_apply, ContinuousLinearMap.add_apply,
+          ContinuousLinearMap.smul_apply, map_add, map_smul]
+        module
       _ ≤ ‖f' (x + h • v + (t * h) • w) - f' x - f'' (h • v + (t * h) • w)‖ * ‖h • w‖ :=
         (ContinuousLinearMap.le_opNorm _ _)
       _ ≤ ε * ‖h • v + (t * h) • w‖ * ‖h • w‖ := by
@@ -169,8 +169,8 @@ theorem Convex.taylor_approx_two_segment {v w : E} (hv : x + v ∈ interior s)
     simp only [g, Nat.one_ne_zero, add_zero, one_mul, zero_div, zero_mul, sub_zero,
       zero_smul, Ne, not_false_iff, zero_pow, reduceCtorEq]
     abel
-  · simp only [Real.norm_eq_abs, abs_mul, add_nonneg (norm_nonneg v) (norm_nonneg w), abs_of_nonneg,
-      hpos.le, mul_assoc, norm_nonneg, abs_pow]
+  · simp (discharger := positivity) only [Real.norm_eq_abs, abs_mul, abs_of_nonneg, abs_pow]
+    ring
 
 /-- One can get `f'' v w` as the limit of `h ^ (-2)` times the alternate sum of the values of `f`
 along the vertices of a quadrilateral with sides `h v` and `h w` based at `x`.
@@ -183,7 +183,6 @@ theorem Convex.isLittleO_alternate_sum_square {v w : E} (h4v : x + (4 : ℝ) •
       fun h => h ^ 2 := by
   have A : (1 : ℝ) / 2 ∈ Ioc (0 : ℝ) 1 := ⟨by norm_num, by norm_num⟩
   have B : (1 : ℝ) / 2 ∈ Icc (0 : ℝ) 1 := ⟨by norm_num, by norm_num⟩
-  have C : ∀ w : E, (2 : ℝ) • w = 2 • w := fun w => by simp only [two_smul]
   have h2v2w : x + (2 : ℝ) • v + (2 : ℝ) • w ∈ interior s := by
     convert s_conv.interior.add_smul_sub_mem h4v h4w B using 1
     module