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Terms & Conditions

Last Updated: March 2026

Welcome to Notebook.

Notebook is a study application designed to help Class 9 & 10 students access notes, important questions (IMP), and previous year question papers (PYQP) for educational purposes. By accessing or using this app, you agree to be bound by these Terms & Conditions. If you do not agree, please discontinue use of the app.

1.
Acceptance of Terms

By continuing to use the Notebook app, you confirm that you have read, understood, and agree to these Terms & Conditions. These terms apply to all users of the app.

2.
Educational Purpose

This app provides educational support content for study purposes only. We strive to maintain accuracy and syllabus alignment with CBSE guidelines. However, we do not guarantee that all information is error-free or fully complete. Students are advised to verify important information with official NCERT textbooks and board guidelines.

2a.
Class 9 Draft Content Notice

Some Class 9 content — particularly Maths — may be based on draft NCERT 2026–27 materials. Chapter lists may differ slightly from the final printed textbook. We recommend cross-checking with your school-issued book.

2b.
Stats and Study Tracking

The app tracks local study data including streaks, chapters saved, exam countdown, and days active. This data is stored on your device only and is not transmitted to our servers. Clearing app/browser data will reset all stats.

3.
No Guarantee of Results

Notebook does not guarantee marks improvement, exam success, or specific academic outcomes. Performance depends entirely on individual preparation, effort, and other external factors. Use of this app is at the student's own discretion.

4.
User Responsibilities

By using Notebook, users agree to:

  • Not misuse, exploit, or attempt to break the app
  • Not attempt unauthorized access, reverse engineering, or scraping
  • Provide accurate information during registration
  • Use the app only for personal educational purposes

Violation of any of these may result in immediate account suspension without refund.

5.
Saved Study Content

Users may save notes, Important Questions (IMP), and Previous Year Papers (PYP) inside the app for personal study access. Saved content is for personal educational use only and must not be redistributed, published, or shared outside the app.

6.
Intellectual Property

All content, branding, notes, design, structure, and features of the Notebook app are the intellectual property of the app owner unless otherwise stated. Unauthorized reproduction, copying, scraping, or distribution of any content — including notes, questions, or UI elements — is strictly prohibited and may result in legal action.

6a.
NCERT / CBSE Disclaimer

Notebook is an independent, student-run educational initiative. It is not affiliated with, endorsed by, or sponsored by NCERT (National Council of Educational Research and Training) or CBSE (Central Board of Secondary Education). "NCERT" and "CBSE" are their respective owners' names and trademarks, used here only to describe the syllabus this content follows. All notes, summaries and questions on Notebook are prepared independently for revision purposes only and are not official NCERT/CBSE publications.

6b.
Report Content / DMCA

If you are a publisher, author, or rights holder and believe content on Notebook infringes your copyright, please email us directly at lumo.feedback@gmail.com with the specific page URL and a description of the material in question. We will review and remove infringing content promptly — there's no need to contact our hosting provider.

7.
Limitation of Liability

To the maximum extent permitted by applicable law, Notebook and its owner shall not be liable for:

  • Academic results, exam performance, or marks
  • Data loss or corruption
  • Technical interruptions or unavailability of the service
  • Indirect, incidental, or consequential damages of any kind
  • Decisions made by users based on app content

Use of the app is entirely at the user's own risk.

8.
Technical Availability

We do not guarantee uninterrupted, error-free, or continuously available service. The app may be updated, modified, or temporarily taken offline without prior notice. We are not responsible for any inconvenience caused by scheduled or unscheduled downtime.

9.
Minor Safety

Notebook is designed for students aged 13 and above. Users under 18 years of age should use this app with awareness of their parent or guardian.

10.
Changes to Terms

We reserve the right to update these Terms & Conditions at any time. Updates will be reflected inside the app. Continued use of the app after updates constitutes acceptance of the revised terms.

11.
Governing Law

These Terms are governed by the laws of India. Any disputes arising out of or related to the use of this app shall fall under the jurisdiction of the courts in India.

12.
Contact Information

For questions, concerns, or refund requests related to these Terms, please contact:

Operated by Rohit Saini

Privacy Policy

Last Updated: March 2026

Notebook respects the privacy of its users.

This policy explains how information may be collected and used when using the Notebook app.

1.
Information We May Collect

The app may collect limited information such as:

  • Name or email address (if login is used)
  • Basic device or browser information
  • Basic usage information within the app
2.
Saved Study Data

Users may save notes, Important Questions (IMP), and Previous Year Papers (PYP) for quick access. This saved study content is associated with the user account or device and is used only to improve the study experience.

2a.
Stats and Local Storage

Study stats including your daily streak, best streak, exam countdown date, chapters saved, and days active are stored entirely on your device using browser local storage. This data:

  • Never leaves your device
  • Is never sent to our servers
  • Is not linked to your account or identity
  • Will be deleted if you clear your browser data or uninstall the app
3.
How Information Is Used

Collected information may be used to:

  • Provide and maintain the app
  • Improve features and performance
  • Allow users to save and access study materials
  • Understand how users interact with the app
4.
Data Protection

Notebook takes reasonable steps to protect user information. However, no online service can guarantee complete security.

5.
Third-Party Services

If the app uses services such as Google login, those services may collect information according to their own privacy policies.

6.
Changes to Privacy Policy

This Privacy Policy may be updated as the app develops. Updates will be reflected inside the app.

7.
Contact

If you have questions about this Privacy Policy, you may contact us at [email protected].

8.
Draft Content Notice

Some Class 9 content in this app may be based on draft NCERT 2026–27 materials. Final chapter lists may vary from printed textbooks.

Operated by Rohit Saini

Grievance Redressal

Last Updated: March 2026

We take user concerns seriously.

Notebook provides this Grievance Redressal Mechanism so that users (or their parents/guardians) can report complaints, concerns, or issues related to the app, its content, or its handling of personal information.

1.
Grievance Officer

In accordance with applicable Indian law, the following person has been designated as the Grievance Officer for Notebook:

2.
What You Can Report

You may reach out to the Grievance Officer for concerns such as:

  • Incorrect, outdated, or inappropriate content within the app
  • Privacy concerns or misuse of personal information
  • Harassment, abusive content, or safety concerns
  • Account, login, or data-related issues
  • Any other complaint regarding the app's functioning
3.
How to File a Grievance

Send an email to the Grievance Officer at the address above with a clear description of your concern. Please include your registered email address and, where relevant, screenshots so the issue can be looked into properly.

4.
Response Timeline

Grievances will be acknowledged within 48 hours of receipt and will be resolved, wherever possible, within 30 days from the date of receipt.

5.
For Parents & Guardians

If you are a parent or guardian of a student using Notebook and have concerns about your child's use of the app, you are welcome to contact the Grievance Officer directly using the details above.

Operated by Rohit Saini

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About Notebook
Notebook
Study Smart. Score Better.
Version 1.0.0 · CBSE Class 9 & 10

Built for students, by someone who understands the exam pressure.

Notebook is a free study app for Class 9 and Class 10 CBSE students. It brings together chapter notes, important questions, and previous year papers — all in one clean, simple app that works even on slow internet.

Our goal is simple: help every student study smarter, revise faster, and feel more confident before exams — without needing expensive coaching or heavy study material.

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What We Cover
  • All 6 CBSE subjects — Science, Maths, English, Hindi, SST, Sanskrit
  • Class 9 & 10 · All subjects as per NCERT syllabus (2026–27)
  • Chapter Notes · Important Questions · Previous Year Papers
  • Save chapters to your personal Library
  • Search across all subjects and chapters
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Notebook tracks your study habits to help you stay motivated.

  • Daily Streak — consecutive days studied
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Notebook is an independent, student-run educational initiative. It is not affiliated with, endorsed by, or sponsored by NCERT or CBSE. NCERT and CBSE own their respective names and materials — they are referenced here only to describe the syllabus this content follows. All notes are original summaries prepared for revision purposes only.

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Class 9th Mathematics Chapter 11 Circles – Notes

Class 9 Maths Chapter 11 – Chord, arc, angle subtended, cyclic quadrilateral. NCERT CBSE notes.

Topics covered in Circles

Frequently asked questions

What topics are covered in Class 9th Mathematics Chapter 11 Circles notes?

This chapter covers: Chord and arc, Angle subtended by chord, Perpendicular from centre, Cyclic quadrilateral, Equal chords.

Are Circles notes free?

Yes, Notebook gives free NCERT CBSE notes for Class 9 Mathematics.

How to prepare Circles for Class 9 Mathematics exams?

Read the Circles notes first, revise the key topics (Chord and arc, Angle subtended by chord, Perpendicular from centre, Cyclic quadrilateral, Equal chords), then practise the important questions and previous year questions (PYQ) for this chapter.

Where can I find Class 9th Mathematics Chapter 11 Circles notes for quick revision?

You are on the right page: this notes page for Circles covers Class 9 Mathematics for the CBSE exam 2026-27. Use the tabs on this chapter for notes, important questions and PYQ.

Is Class 9th Mathematics Chapter 11 Circles important for the CBSE exam 2026-27?

Circles is part of the Class 9 Mathematics NCERT CBSE syllabus. Notebook gives notes, important questions and PYQs for it, free.

Also see: Class 9th Mathematics Chapter 11 Circles Important Questions · Class 9th Mathematics Chapter 11 Circles PYQ

Circles

Surface Area of Solids

Cuboid: LSA = 2h(l+b), TSA = 2(lb+bh+hl). Cube (side a): TSA = 6a². Cylinder (r,h): CSA = 2πrh, TSA = 2πr(r+h). Cone (r,l,h): CSA = πrl, TSA = πr(r+l), where l = √(r²+h²). Sphere (r): SA = 4πr². Hemisphere: CSA = 2πr², TSA = 3πr².

Volume of Solids

Cuboid: V = lbh. Cube: V = a³. Cylinder: V = πr²h. Cone: V = ⅓πr²h. Sphere: V = (4/3)πr³. Hemisphere: V = (2/3)πr³. Relation: Volume of cone = ⅓ × Volume of cylinder (same base and height). Volume of sphere = (2/3) × Volume of cylinder (same radius and height equal to diameter).

Practical Applications

Surface area is used to calculate material needed to cover or wrap an object. Volume gives the capacity. Real-life examples: finding the volume of a water tank (cylinder), material for a conical tent (CSA of cone), painting a room (TSA of cuboid minus openings). Always use consistent units.

Want to save your progress? Open the Notebook app →

Other chapters in Mathematics · Class 9
01
🔵
Coordinate Geometry Class 9 · Mathematics
02
📊
Polynomials Class 9 · Mathematics
03
#️⃣
Number Systems Class 9 · Mathematics
04
📐
Euclid's Geometry Class 9 · Mathematics
05
📏
Lines and Angles Class 9 · Mathematics
06
🔢
Sequences and Progressions Class 9 · Mathematics
07
🔺
Triangles Class 9 · Mathematics
08
📐
Mensuration (Area) Class 9 · Mathematics
View all Mathematics chapters →
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