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Triangles — Flashcards

ICSE · Class 9 · Mathematics

30 flashcards for Triangles (ICSE Class 9 Mathematics) to test yourself on key terms and facts. Sample: "Problem: In triangle ABC, side AC is greater"

40 questions30 flashcards5 formulas & key relations5 concepts

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A labeled diagram showing the vertices, sides, and angles of a basic triangle ABC.
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30 Flashcards·
Side-angle relationIsosceles triangle propertyAngle sum propertyRight triangle anglesAngle sum corollary
Card 1Side-angle relation

Problem: In triangle ABC, side AC is greater than side AB. Which angle is greater: angle B or angle C?

Answer

Step 1: The greater side has the greater angle opposite to it. Step 2: Side AC is opposite angle B. Step 3: Side AB is opposite angle C. Answer: angle B is greater than angle C.

Card 2Side-angle relation

Problem: In triangle ABC, angle C is greater than angle A. Which side is longer: AB or BC?

Answer

Step 1: The greater angle has the greater side opposite to it. Step 2: Angle C is opposite side AB. Step 3: Angle A is opposite side BC. Answer: AB is longer than BC.

Card 3Isosceles triangle property

Problem: In triangle ABC, AB = AC. What can be said about angle B and angle C?

Answer

Step 1: If any two sides of a triangle are equal, the angles opposite them are equal. Step 2: AB = AC. Step 3: Angle C is opposite AB and angle B is opposite AC. Answer: angle B = angle C.

Card 4Isosceles triangle property

Problem: In triangle ABC, angle B = angle C. What can be said about AB and AC?

Answer

Step 1: If any two angles of a triangle are equal, the sides opposite them are equal. Step 2: Angle B = angle C. Step 3: Side AC is opposite angle B and side AB is opposite angle C. Answer: AB = AC.

Card 5Angle sum property

Problem: Find the third angle of a triangle if angle A = 50° and angle B = 60°.

Answer

Step 1: Use the angle sum property. Step 2: angle A + angle B + angle C = 180°. Step 3: 50° + 60° + angle C = 180°. Step 4: angle C = 180° - 110° = 70°. Answer: 70°.

Card 6Angle sum property

Formula: What is the angle sum property of a triangle?

Answer

Formula: angle A + angle B + angle C = 180°. Meaning: The three interior angles of a triangle always add up to 180°. Quick example: If two angles are 40° and 65°, the third angle is 75° because 180° -…

Card 7Right triangle angles

Problem: One angle of a triangle is 90° and another is 35°. Find the third angle.

Answer

Step 1: The sum of angles in a triangle is 180°. Step 2: 90° + 35° + angle C = 180°. Step 3: angle C = 180° - 125° = 55°. Answer: 55°. Check: 90° + 35° + 55° = 180°.

Card 8Angle sum corollary

Problem: If one angle of a triangle is 100°, can the triangle have another obtuse angle?

Answer

Step 1: A triangle cannot have more than one obtuse angle. Step 2: The angles of a triangle add up to 180°. Step 3: After one angle is 100°, only 80° is left for the other two angles. Step 4: Two obtu…

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Frequently Asked Questions

What are the important topics in Triangles for ICSE Class 9 Mathematics?
Key topics in Triangles include Basic Ideas and Side-Angle Relations, Medians, Centroid, Altitudes and Orthocentre, Angle Sum, Exterior Angles and Corollaries, Congruent Triangles and CPCTC. Study these first, then practise questions on each for Class 9 exams.
How many flashcards are available for Triangles?
There are 30 flashcards for Triangles covering key definitions, facts and ideas. A few sample cards are shown on this page.
How should I revise Triangles for Class 9 exams?
Learn the core ideas first, then work through the 40 practice questions on 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.

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