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Chapter 2 of 12
Flashcards

Triangles

Karnataka Board · Class 9 · Mathematics

Flashcards for Triangles — Karnataka Board Class 9 Mathematics. Quick Q&A cards covering key concepts, definitions, and formulas.

45 questions20 flashcards5 concepts
20 Flashcards
Card 1Properties of Isosceles Triangle

In triangle ABC, AB = 5 cm, AC = 5 cm, and BC = 6 cm. Find the measures of angles B and C.

Answer

Step 1: Identify triangle type → AB = AC, so triangle ABC is isosceles. Step 2: Apply isosceles triangle property → Angles opposite to equal sides are equal, so ∠B = ∠C. Step 3: Let ∠B = ∠C = x. Step

Card 2SAS Congruence Rule

Prove that triangles ABC and DEF are congruent if AB = DE = 4 cm, BC = EF = 3 cm, and ∠B = ∠E = 90°.

Answer

Step 1: Identify given information → AB = DE = 4 cm, BC = EF = 3 cm, ∠B = ∠E = 90°. Step 2: Check congruence rule → We have two sides and included angle. Step 3: Apply SAS rule → In △ABC and △DEF: AB

Card 3Properties of Isosceles Triangle

In triangle PQR, PQ = 7 cm, QR = 7 cm, and PR = 8 cm. If QS is the altitude to PR, find the length of PS.

Answer

Step 1: Identify triangle type → PQ = QR = 7 cm, so triangle PQR is isosceles. Step 2: Property of isosceles triangle → Altitude from vertex angle bisects the base. Step 3: Since QS is altitude to PR,

Card 4ASA Congruence Rule

When do you use the ASA congruence rule? Give a worked example.

Answer

Use ASA when: Two angles and included side of one triangle equal two angles and included side of another triangle. Example: In △ABC and △XYZ, if ∠A = ∠X = 60°, ∠B = ∠Y = 50°, and AB = XY = 5 cm. Step

Card 5Area of Triangle

Solve: In △ABC, AB = AC = 10 cm and BC = 12 cm. Find the area of the triangle.

Answer

Step 1: Identify triangle type → AB = AC, so isosceles triangle. Step 2: Draw altitude AD to BC → D bisects BC, so BD = DC = 6 cm. Step 3: Use Pythagoras in △ABD → AD² + BD² = AB², so AD² + 6² = 10²,

Card 6SSS Congruence Rule

Prove: If two triangles have all three sides equal, they are congruent. State the rule used.

Answer

Step 1: State the rule → SSS (Side-Side-Side) Congruence Rule. Step 2: Given → In △ABC and △DEF: AB = DE, BC = EF, CA = FD. Step 3: Apply SSS rule → Since all three corresponding sides are equal, △ABC

Card 7Right Triangle and Pythagoras

In right triangle ABC with ∠C = 90°, if AB = 13 cm and BC = 5 cm, find AC and verify using congruence.

Answer

Step 1: Apply Pythagoras theorem → AB² = AC² + BC², so 13² = AC² + 5². Step 2: Calculate AC → 169 = AC² + 25, so AC² = 144, therefore AC = 12 cm. Step 3: Verify dimensions → We have a 5-12-13 right tr

Card 8RHS Congruence Rule

When do you use RHS congruence rule? Solve: Two right triangles have hypotenuse 10 cm and one side 6 cm. Are they congruent?

Answer

Use RHS when: Two right triangles have equal hypotenuse and one equal side. Solution: Step 1: Given → Both triangles have hypotenuse = 10 cm, one side = 6 cm, and one right angle. Step 2: Find third s

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Frequently Asked Questions

What are the important topics in Triangles for Karnataka Board Class 9 Mathematics?

Triangles covers several key topics that are frequently asked in Karnataka Board Class 9 board exams. Focus on the core concepts listed on this page and practise related questions to build confidence.

Start by understanding all key concepts. Practise previous year questions from this chapter. Revise formulas and definitions regularly. Use flashcards for quick revision before the exam.

There are 20 flashcards for Triangles covering key definitions, formulas, and concepts. Use them daily for 10–15 minutes for best results.

Sources & Official References

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