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Chapter 15 of 22
Flashcards

Circles

ICSE · Class 10 · Mathematics

Flashcards for Circles — ICSE Class 10 Mathematics. Quick Q&A cards covering key concepts, definitions, and formulas.

40 questions28 flashcards5 concepts

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A labeled diagram illustrating the definition of a circle with its center and radius.
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28 Flashcards
Card 1Basic circle concept

A circle has centre O and radius 7 cm. Write the formula for a circle and state why the radius is always positive.

Answer

Formula idea: A circle is the set of all points at a constant distance from a fixed point. Step 1: The fixed point is called the centre. Step 2: The constant distance is called the radius. Step 3: The

Card 2Degree measure theorem

Find the degree measure of arc PQ if the angle subtended by arc PQ at point R on the circle is 35°.

Answer

Use the degree measure theorem. Step 1: Degree measure of arc PQ = 2 × angle subtended at the point on the circle. Step 2: Arc PQ = 2 × 35°. Step 3: Arc PQ = 70°. Answer: 70°

Card 3Angles in the same segment

Why are angles in the same segment of a circle equal? Give a quick reasoning from the angle theorem.

Answer

Step 1: Two angles in the same segment subtend the same arc. Step 2: Each angle at the circle equals half the angle subtended by the same arc at the centre. Step 3: Since both depend on the same centr

Card 4Angle in a semicircle

A chord PQ is a diameter. Find the angle subtended by PQ at any point R on the remaining part of the circle.

Answer

Use the angle in a semicircle theorem. Step 1: A diameter subtends a straight angle at the centre, so ∠POQ = 180°. Step 2: Angle at the circle is half the angle at the centre. Step 3: ∠PRQ = 180° ÷ 2

Card 5Same segment theorem

A point R on a circle sees chord PQ under 48°. What is the angle seen by another point S in the same segment on the same side of PQ?

Answer

Step 1: Angles in the same segment of a circle are equal. Step 2: So ∠PRQ = ∠PSQ. Step 3: Given ∠PRQ = 48°. Answer: ∠PSQ = 48°

Card 6Converse of semicircle theorem

Show that if an angle subtended by an arc is 90° at a point on the circle, then the arc is a semicircle.

Answer

Step 1: Let the arc subtend angle 90° at a point on the circle. Step 2: Angle at the centre = 2 × angle at the circle. Step 3: Central angle = 2 × 90° = 180°. Step 4: A 180° central angle means the en

Card 7Concyclic points

Three points P, Q, and R lie on a circle. Point S is on the same side of line PQ and ∠PRQ = ∠PSQ. What can be said about P, Q, R, S?

Answer

Step 1: A line segment subtending equal angles at two points on the same side implies the four points are concyclic. Step 2: Since ∠PRQ = ∠PSQ, points P, Q, R, S lie on one circle. Answer: The four po

Card 8Cyclic quadrilateral angles

A cyclic quadrilateral ABCD has ∠A = 72°. Find ∠C.

Answer

Use opposite angles of a cyclic quadrilateral. Step 1: ∠A + ∠C = 180°. Step 2: 72° + ∠C = 180°. Step 3: ∠C = 180° - 72° = 108°. Answer: 108°

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Frequently Asked Questions

What are the important topics in Circles for ICSE Class 10 Mathematics?
Circles covers several key topics that are frequently asked in ICSE Class 10 board exams. Focus on the core concepts listed on this page and practise related questions to build confidence.
How to score full marks in Circles — ICSE Class 10 Mathematics?
Understand the core concepts first, then work through the 40 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 Circles?
There are 28 flashcards for Circles covering key definitions, formulas, and concepts. Use them daily for 10–15 minutes for best results.

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