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Formula Sheet

Isosceles Triangles — Formula Sheet

ICSE · Class 9 · Mathematics

8 formulas from Isosceles Triangles (ICSE Class 9 Mathematics) on one page, grouped by topic. Part of the ICSE Class 9 Mathematics syllabus.

35 questions20 flashcards8 formulas & key relations5 concepts

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A labeled diagram illustrating an isosceles triangle with two equal sides and the angles opposite to them also being equal. Includes the definition of an equilateral triangle as a special case.
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8 Entries · 3 Sections

Formulas and Key Relations

Main Theorems

If two sides of a triangle are equal, the angles opposite to them are also equal.

If two angles of a triangle are equal, the sides opposite to them are also equal.

Solved-Pattern Results

angle BAD : angle ADB = 3 : 1

Ext. angle CEA = the sum of two interior opposite angles = 32° + 36° = 68°

a + 80° + 80° = 180°

angle OBC = angle OBA = angle OCB = angle OCA

Important theorem proofs

In Theorem 1, angle ADB = angle ADC = 90° because AD is perpendicular to BC.

In Theorem 1, AB = AC, AD = AD, and angle ADB = angle ADC.

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Frequently Asked Questions

What are the important topics in Isosceles Triangles for ICSE Class 9 Mathematics?
Key topics in Isosceles Triangles include Core ideas and definitions, Important theorem proofs, Other properties of isosceles triangles, Solved problem patterns to remember. Study these first, then practise questions on each for Class 9 exams.
How many formulas are in Isosceles Triangles?
This sheet lists 8 formulas from Isosceles Triangles, grouped by topic. Learn what each symbol stands for so you can apply the formula, not just recall it.
How should I revise Isosceles Triangles for Class 9 exams?
Learn the core ideas first, then work through the 35 practice questions on Isosceles Triangles. Revise definitions regularly and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

More resources for Isosceles Triangles

All ICSE Class 9 Mathematics Formula Sheet

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