Circle
ICSE · Class 9 · Mathematics
Flashcards for Circle — ICSE Class 9 Mathematics. Quick Q&A cards covering key concepts, definitions, and formulas.
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Get startedSolve: A chord of length 6 cm is drawn in a circle of radius 5 cm. Find the distance of the chord from the centre.
Answer
Step 1: Half of the chord = 6/2 = 3 cm. Step 2: Use OA² = OP² + AP². Step 3: 5² = OP² + 3². Step 4: 25 = OP² + 9. Step 5: OP² = 16, so OP = 4 cm. Answer: The distance from the centre is 4 cm.
Solve: A chord of length 8 cm is at a distance of 3 cm from the centre. Find the radius of the circle.
Answer
Step 1: Half of the chord = 8/2 = 4 cm. Step 2: Use OA² = OP² + AP². Step 3: OA² = 3² + 4². Step 4: OA² = 9 + 16 = 25. Step 5: OA = 5 cm. Answer: The radius is 5 cm.
Solve: The radius of a circle is 17 cm and the perpendicular from the centre to a chord is 8 cm. Find the length of the chord.
Answer
Step 1: Let half the chord be x cm. Step 2: Use OA² = OP² + AP². Step 3: 17² = 8² + x². Step 4: 289 = 64 + x². Step 5: x² = 225, so x = 15 cm. Step 6: Full chord = 2 × 15 = 30 cm. Answer: The chord is…
Solve: A chord of length 24 cm is 5 cm from the centre. Find the radius of the circle.
Answer
Step 1: Half the chord = 24/2 = 12 cm. Step 2: Use OA² = OP² + AP². Step 3: r² = 5² + 12². Step 4: r² = 25 + 144 = 169. Step 5: r = 13 cm. Answer: The radius is 13 cm.
Solve: In the same circle, one chord is 24 cm long at a distance of 5 cm from the centre. Another chord is at a distance of 12 cm from the centre. Find the length of the second chord.
Answer
Step 1: From the first chord, half-length = 12 cm. Step 2: Radius = 13 cm from OA² = OP² + AP². Step 3: For the second chord, let half-length be x cm. Step 4: Use 13² = 12² + x². Step 5: 169 = 144 + x…
Solve: Two parallel chords in a circle have lengths 30 cm and 16 cm. The radius is 17 cm. Find the distance between the chords when they are on opposite sides of the centre.
Answer
Step 1: For the 30 cm chord, half-length = 15 cm. Step 2: Distance from centre = √(17² - 15²) = √(289 - 225) = √64 = 8 cm. Step 3: For the 16 cm chord, half-length = 8 cm. Step 4: Distance from centre…
Solve: Two parallel chords in a circle have lengths 30 cm and 16 cm. The radius is 17 cm. Find the distance between the chords when they are on the same side of the centre.
Answer
Step 1: Distance of the 30 cm chord from centre = 8 cm. Step 2: Distance of the 16 cm chord from centre = 15 cm. Step 3: On the same side, distance between chords = 15 - 8 = 7 cm. Answer: The distance…
Why is a line from the centre that bisects a chord perpendicular to the chord?
Answer
Take the two triangles formed by joining the centre to the two ends of the chord and to its midpoint. Step 1: The two radii are equal. Step 2: The two halves of the chord are equal. Step 3: The shared…
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