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.
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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.
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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.
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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
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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.
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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.
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Contact Information
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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
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Data Protection
Notebook takes reasonable steps to protect user information. However, no online service can guarantee complete security.
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Third-Party Services
If the app uses services such as Google login, those services may collect information according to their own privacy policies.
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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:
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.
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 10th Mathematics Chapter 6 Triangles – Notes
What topics are covered in Class 10th Mathematics Chapter 6 Triangles notes?
This chapter covers: Basic proportionality theorem, Similarity of triangles, AA, SSS, SAS similarity, Pythagoras theorem.
Are Triangles notes free?
Yes, Notebook gives free NCERT CBSE notes for Class 10 Mathematics.
How to prepare Triangles for Class 10 Mathematics exams?
Read the Triangles notes first, revise the key topics (Basic proportionality theorem, Similarity of triangles, AA, SSS, SAS similarity, Pythagoras theorem), then practise the important questions and previous year questions (PYQ) for this chapter.
Where can I find Class 10th Mathematics Chapter 6 Triangles notes for quick revision?
You are on the right page: this notes page for Triangles covers Class 10 Mathematics for the CBSE exam 2026-27. Use the tabs on this chapter for notes, important questions and PYQ.
Is Class 10th Mathematics Chapter 6 Triangles important for the CBSE exam 2026-27?
Triangles is part of the Class 10 Mathematics NCERT CBSE syllabus. Notebook gives notes, important questions and PYQs for it, free.
Two triangles are similar if their corresponding angles are equal and corresponding sides are proportional. Similar ≠ congruent. Congruent triangles are always similar but not vice versa. The ratio of areas of two similar triangles = square of the ratio of their corresponding sides.
Criteria for Similarity
AA (Angle-Angle): two angles equal → triangles similar. SSS: all three sides proportional → similar. SAS: one angle equal and adjacent sides proportional → similar. These are the main similarity criteria used to solve problems.
Basic Proportionality Theorem (Thales Theorem)
If a line is drawn parallel to one side of a triangle intersecting the other two sides, it divides those sides in the same ratio. If DE ∥ BC in △ABC, then AD/DB = AE/EC. Converse is also true.
Pythagoras Theorem
In a right-angled triangle, the square of the hypotenuse = sum of squares of the other two sides: AC² = AB² + BC². Converse: if AC² = AB² + BC², angle B = 90°. Used extensively in coordinate geometry and real-life problems.
Basic Proportionality Theorem (Thales Theorem)
Statement: If a line is drawn parallel to one side of a triangle, it divides the other two sides proportionally. Formally: In ΔABC, if DE ∥ BC and D is on AB, E is on AC, then AD/DB = AE/EC. Converse: If a line divides two sides of a triangle in the same ratio, it is parallel to the third side. Proof uses areas of triangles with equal height. This theorem is the foundation for similar triangles and is extremely important for board exams.
Criteria for Similarity of Triangles
Two triangles are similar if their corresponding angles are equal and corresponding sides are proportional. Criteria: (1) AA (Angle-Angle): two pairs of equal angles → triangles are similar; (2) SSS: all three sides proportional → similar; (3) SAS: two sides proportional and included angle equal → similar. In similar triangles ΔABC ~ ΔPQR: AB/PQ = BC/QR = CA/RP and corresponding angles are equal. Ratio of areas of similar triangles = square of ratio of corresponding sides.
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