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Chapter 4 of 9
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Geometry

Tamil Nadu Board · Class 9 · Mathematics

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

42 questions25 flashcards5 concepts

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25 Flashcards
Card 1Angles - Complementary and Supplementary

Two angles are complementary. If one angle is 35°, find the other angle.

Answer

Step 1: Recall that complementary angles sum to 90°. Step 2: Let the unknown angle = x Step 3: 35° + x = 90° Step 4: x = 90° - 35° = 55° Answer: The other angle is 55°

Card 2Angles - Linear Pairs

Two angles form a linear pair. If one angle is 127°, find the other angle.

Answer

Step 1: Recall that angles in a linear pair sum to 180°. Step 2: Let the second angle = x Step 3: 127° + x = 180° Step 4: x = 180° - 127° = 53° Answer: The other angle is 53°

Card 3Angles - Vertically Opposite Angles

Two lines intersect. One of the vertically opposite angles is 68°. Find all four angles formed.

Answer

Step 1: Vertically opposite angles are equal. Step 2: First pair of vertically opposite angles = 68° each Step 3: The adjacent angles form linear pairs with 68°. Step 4: Adjacent angle = 180° - 68° =

Card 4Triangles - Angle Sum Property

In a triangle, one angle is 52° and another is 63°. Find the third angle.

Answer

Step 1: Recall the angle sum property of triangles: Sum of all angles = 180° Step 2: Let the third angle = x Step 3: 52° + 63° + x = 180° Step 4: 115° + x = 180° Step 5: x = 180° - 115° = 65° Answer:

Card 5Triangles - Angle Sum Property

The angles of a triangle are in the ratio 1:2:3. Find all three angles.

Answer

Step 1: Let the angles be x, 2x, and 3x (based on ratio 1:2:3) Step 2: Apply angle sum property: x + 2x + 3x = 180° Step 3: 6x = 180° Step 4: x = 30° Step 5: The three angles are: - First angle: x = 3

Card 6Triangles - Exterior Angle Property

In triangle ABC, if an exterior angle at C is 110°, and angle A = 45°, find angle B.

Answer

Step 1: Recall the exterior angle theorem: Exterior angle = sum of two non-adjacent interior angles Step 2: Apply the theorem: Exterior angle at C = angle A + angle B Step 3: 110° = 45° + angle B Step

Card 7Triangles - Congruence Rules

When do you use the SSS (Side-Side-Side) congruence rule? Give an example.

Answer

Use SSS when you know all three sides of both triangles are equal. Example: Triangle ABC has sides AB = 5 cm, BC = 6 cm, AC = 7 cm Triangle DEF has sides DE = 5 cm, EF = 6 cm, DF = 7 cm Since all thre

Card 8Triangles - Congruence Rules

Triangle ABC has AB = 6 cm, angle A = 50°, and AC = 5 cm. Triangle PQR has PQ = 6 cm, angle P = 50°, and PR = 5 cm. Are they congruent? Justify.

Answer

Step 1: Identify the given information: - Triangle ABC: AB = 6 cm, AC = 5 cm, angle A = 50° (angle between the two sides) - Triangle PQR: PQ = 6 cm, PR = 5 cm, angle P = 50° (angle between the two sid

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Frequently Asked Questions

What are the important topics in Geometry for Tamil Nadu Board Class 9 Mathematics?
Key topics in Geometry include Geometry Concepts Overview, Geometry Chapter 4 – Complete Concept Overview, Complete Geometry Concept Map. These are the concepts Tamil Nadu Board Class 9 examiners draw on most — study them first, then practise related questions.
How to score full marks in Geometry — Tamil Nadu Board Class 9 Mathematics?
Understand the core concepts first, then work through the 42 practice questions available for this chapter. Revise formulas and definitions regularly, and use flashcards for quick recall before the exam.
How many flashcards are available for Geometry?
There are 25 flashcards for Geometry covering key definitions, formulas, and concepts. Use them daily for 10–15 minutes for best results.

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

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