Assume that limh-0 (h) exists. Show that limh-04 (h) show that if f is differentiable at a then There are two parts: f'(x) = lim h→0 f (x + h) − f (x − h) 2h = lim-0 (-h). Use this to

Advanced Engineering Mathematics
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Chapter2: Second-order Linear Odes
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Please answer both parts clearly. It's a practice question, and include a picture of your solution

 

**Transcription for Educational Website**

---

**Theorem Proof and Differentiation**

Assume that \(\lim_{h \to 0} \varphi(h)\) exists. Show that \(\lim_{h \to 0} \varphi(h) = \lim_{h \to 0} \varphi(-h)\). Use this to show that if \(f\) is differentiable at \(x\) then

\[
f'(x) = \lim_{h \to 0} \frac{f(x + h) - f(x - h)}{2h}.
\]

**There are two parts:**

1. **Assume that \(\lim_{h \to 0} \varphi(h) = L\)**. Argue that for any \(\epsilon > 0\), there is a \(\delta > 0\) such that 
\[
|\varphi(h) - L| < \epsilon \quad \text{whenever} \quad 0 < |h - 0| < \delta.
\]

2. **Change the variable \(h' = -h\) to prove that**

\[
\lim_{h' \to 0} \varphi(-h') = L.
\]

**Consider** \(\varphi(h) = \frac{f(x+h) - f(x)}{h}\), \(h \neq 0\). Notice that \(f'(x) = \lim_{h \to 0} \varphi(h)\). Use this and the first part to show that

\[
f'(x) = \frac{1}{2} \left( \lim_{h \to 0} \varphi(h) + \lim_{h \to 0} \varphi(-h) \right) = \lim_{h \to 0} \frac{f(x + h) - f(x - h)}{2h}.
\]

---

**Explanation of Diagrams/Graphs:**

There are no diagrams or graphs present in the provided text. This content is purely mathematical and textual in nature, focusing on proving a theorem related to limits and differentiability.
Transcribed Image Text:**Transcription for Educational Website** --- **Theorem Proof and Differentiation** Assume that \(\lim_{h \to 0} \varphi(h)\) exists. Show that \(\lim_{h \to 0} \varphi(h) = \lim_{h \to 0} \varphi(-h)\). Use this to show that if \(f\) is differentiable at \(x\) then \[ f'(x) = \lim_{h \to 0} \frac{f(x + h) - f(x - h)}{2h}. \] **There are two parts:** 1. **Assume that \(\lim_{h \to 0} \varphi(h) = L\)**. Argue that for any \(\epsilon > 0\), there is a \(\delta > 0\) such that \[ |\varphi(h) - L| < \epsilon \quad \text{whenever} \quad 0 < |h - 0| < \delta. \] 2. **Change the variable \(h' = -h\) to prove that** \[ \lim_{h' \to 0} \varphi(-h') = L. \] **Consider** \(\varphi(h) = \frac{f(x+h) - f(x)}{h}\), \(h \neq 0\). Notice that \(f'(x) = \lim_{h \to 0} \varphi(h)\). Use this and the first part to show that \[ f'(x) = \frac{1}{2} \left( \lim_{h \to 0} \varphi(h) + \lim_{h \to 0} \varphi(-h) \right) = \lim_{h \to 0} \frac{f(x + h) - f(x - h)}{2h}. \] --- **Explanation of Diagrams/Graphs:** There are no diagrams or graphs present in the provided text. This content is purely mathematical and textual in nature, focusing on proving a theorem related to limits and differentiability.
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