[DOCS] Add Diagrams to EM1 Chapter 3 — Ordinary Differential Equations

[SG170]

📌 Issue: Add Diagrams to EM1 Chapter 3 — Ordinary Differential Equations

Description

The Chapter 3 notes for Engineering Mathematics I (/sem1/em1/ch3) are currently text-only. Each section has a placeholder comment like Diagram: filename.png but no actual diagrams have been added yet.

This issue tracks adding visual diagrams for all placeholder sections to improve student understanding.

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Sections needing diagrams

• First Order Exact Equations → exact-ode-flow.png
• Second Order Linear Equations with Constant Coefficients → characteristic-roots.png

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Proposed Solution

Create clear, labeled SVG/PNG diagrams for each of the above topics and replace the placeholder comments with proper <img> tags.

Diagrams will cover:

• Flowchart for solving exact ODEs (check exactness → find potential function → solve)
• Characteristic root cases: real distinct, real equal, and complex roots with their solution forms

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Why this matters

ODE solution methods are step-by-step procedures. Flowcharts and diagrams showing the decision logic and root cases make it significantly easier for students to apply the right method during exams.

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Would like to work on this

I'd like to take this up as part of GSSoC. Please assign this issue to me.

Note to maintainer: If there's a preferred folder path for images or a specific format (SVG vs PNG, size/style guidelines), please let me know before I open the PR.