Geometry: Circles and Chords
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Questions and Answers

What is the distance between Reshma and Mandip?

  • 12 cm
  • 9.6 cm (correct)
  • 6 cm
  • 10.4 cm

What is the length of the string of each toy telephone?

  • 10 m
  • 30 m
  • 20√3 m (correct)
  • 40√2 m

Which theorem describes the relationship between angles subtended by an arc at the center and a point on the circle?

  • The Pythagorean theorem
  • Theorem 9.7 (correct)
  • Isosceles triangle theorem
  • Congruent chords theorem

In ΔROP, if angle ROP is x and angle MOP is also x, what can be inferred about OP?

<p>OP bisects RM (D)</p> Signup and view all the answers

If two chords in a circle are equal, what can be concluded about the arcs they subtend?

<p>The arcs are congruent (A)</p> Signup and view all the answers

In triangle AOP, if OA and OP are equal to the radius, which statement is true?

<p>Triangle AOP is isosceles. (D)</p> Signup and view all the answers

From the calculation provided, what is the value of y when $y^2 = 25 - x^2$ and $x^2 = 1.4$?

<p>4.8 cm (C)</p> Signup and view all the answers

If OP is perpendicular to RM, what does this indicate about angles RPO and MPO?

<p>Both are equal to 90 degrees (A)</p> Signup and view all the answers

What is the measure of angle ∠BCD if ∠DAB = 100°?

<p>80° (D)</p> Signup and view all the answers

In a cyclic quadrilateral, which pair of opposite angles is always true?

<p>They are supplementary. (B)</p> Signup and view all the answers

What is the value of the angle subtended by a chord equal to the radius at a point on the minor arc?

<p>30° (B)</p> Signup and view all the answers

If angle ∠BOC = 30° and angle ∠AOB = 60°, what is angle ∠ADC?

<p>45° (A)</p> Signup and view all the answers

What property do equal chords of congruent circles share regarding the angles they subtend at the center?

<p>They subtend equal angles. (B)</p> Signup and view all the answers

What angles are formed when the internal angle bisectors of a quadrilateral are drawn?

<p>They are supplementary in pairs. (B)</p> Signup and view all the answers

According to Theorem 9.3, what does the perpendicular from the center of a circle to a chord do?

<p>Bisects the chord. (D)</p> Signup and view all the answers

When proving that angle ∠ABD equals 90°, what property is being used?

<p>Angle in a semicircle. (D)</p> Signup and view all the answers

What can be concluded from the congruency of triangles formed by a radius and a chord in a circle?

<p>The chords are always congruent. (C)</p> Signup and view all the answers

What is the total of angles ∠FEH and ∠FGH in a cyclic quadrilateral formed by angle bisectors?

<p>180° (D)</p> Signup and view all the answers

Which theorem states that equal chords of a circle are equidistant from the center?

<p>Theorem 9.5 (B)</p> Signup and view all the answers

In triangle ABO, where OA and OB are radii, what type of triangle is formed if AB equals the radius?

<p>Equilateral triangle (D)</p> Signup and view all the answers

What does Theorem 9.6 imply about chords that are equidistant from the center of the circle?

<p>They are equal in length. (C)</p> Signup and view all the answers

In a circle, what is the implication of the point where two chords intersect in terms of their lengths?

<p>Their lengths depend on the angles they create. (C)</p> Signup and view all the answers

In the proof of Theorem 9.3, which triangle congruence rule is applied?

<p>SSS congruence rule (C)</p> Signup and view all the answers

When drawing perpendiculars from the center of a circle to equal chords, what relationship is established regarding their lengths?

<p>They are equal. (C)</p> Signup and view all the answers

What is the definition of a chord in a circle?

<p>A line segment joining any two points on the circle. (A)</p> Signup and view all the answers

Which statement about a semicircle is correct?

<p>It is an arc that is exactly half the circumference of the circle. (B)</p> Signup and view all the answers

What is the length of the common chord formed by two circles of radii 5 cm and 3 cm intersecting with a distance of 4 cm between their centers?

<p>6 cm (B)</p> Signup and view all the answers

What does the theorem state regarding equal chords in a circle?

<p>Equal chords of a circle subtend equal angles at the center. (D)</p> Signup and view all the answers

In the scenario where two equal chords, AB and CD, intersect within a circle at point E, what can be concluded about the segments AE and DE?

<p>AE equals DE (A)</p> Signup and view all the answers

In terms of arcs, how is a minor arc defined?

<p>An arc smaller than a semicircle. (C)</p> Signup and view all the answers

If two equal chords of a circle intersect at point E, what property do the angles formed by the line joining point E to the center of the circle have with respect to the chords?

<p>They are equal (B)</p> Signup and view all the answers

What is the relationship between a major segment and a chord in a circle?

<p>It's the region between the chord and the major arc. (C)</p> Signup and view all the answers

What is demonstrated when a line intersects two concentric circles at points A, B, C, and D?

<p>AB equals CD (B)</p> Signup and view all the answers

What can be concluded if two angles subtended by chords at the center of the circle are equal?

<p>The chords are equal. (A)</p> Signup and view all the answers

What geometric shape is formed by connecting the centers of two intersecting circles and their common chord?

<p>Triangle (A)</p> Signup and view all the answers

If a radius of a circle measures 5 cm, what is the length of the diameter?

<p>10 cm (B)</p> Signup and view all the answers

Which of the following describes a sector of a circle?

<p>The area enclosed by an arc and the two radii connecting the center. (D)</p> Signup and view all the answers

When finding the segments of equal chords, which condition must be met for two segments to be equal?

<p>The chords must be equal in length and form right angles (A)</p> Signup and view all the answers

In the context of intersecting circles, what does BR represent in the problem's solution?

<p>Segment from center to R, on the common chord (B)</p> Signup and view all the answers

Which triangle property is utilized to show congruency when proving angles at the point of intersection of equal chords?

<p>RHS (Right angle-Hypotenuse-Side) congruence rule (B)</p> Signup and view all the answers

If the angle subtended by an arc at the center of a circle is 200°, what is the angle subtended at any point on the remaining part of the circle?

<p>160° (A)</p> Signup and view all the answers

In triangle ABC, if ∠ABC = 69° and ∠ACB = 31°, what is ∠BAC?

<p>80° (C)</p> Signup and view all the answers

Given four points A, B, C, and D on a circle where AC and BD intersect at E, if ∠BEC = 130° and ∠ECD = 20°, what is ∠BAC?

<p>110° (D)</p> Signup and view all the answers

In a cyclic quadrilateral ABCD, if ∠BDC = 30° and ∠DBC = 70°, what is the measure of ∠BCD?

<p>80° (B)</p> Signup and view all the answers

What can be concluded if the diagonals of a cyclic quadrilateral are diameters of the circle?

<p>It is a rectangle. (B)</p> Signup and view all the answers

In a cyclic quadrilateral ABCD, which condition guarantees that it is cyclic?

<p>The non-parallel sides are equal. (B)</p> Signup and view all the answers

In triangle ABC, if sides AB and AC are equal, which of the following is true regarding the angles?

<p>∠BCA = ∠CAB (C)</p> Signup and view all the answers

If two non-parallel sides of a trapezium are equal and the angles at the base are supplementary, what can be inferred?

<p>The trapezium is cyclic. (D)</p> Signup and view all the answers

Flashcards

Circle

A collection of all points in a plane that are a fixed distance from a fixed point on the plane.

Diameter

A line segment connecting two points on a circle that passes through the center.

Chord

A line segment connecting two points on a circle.

Arc

Part of the circle between two points.

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Semicircle

An arc formed when the endpoints of the arc are the endpoints of the diameter.

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Minor Arc

An arc that is smaller than a semicircle.

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Major Arc

An arc that is larger than a semicircle.

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Sector

The area enclosed by an arc and the two radii connecting the center to the endpoints of the arc.

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Equal Chords Subtend Equal Angles

In congruent circles, chords of equal length create equal angles at their respective centers.

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Perpendicular from Center to Chord

A line drawn from the center of a circle perpendicular to a chord bisects the chord.

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Bisecting Chord and Perpendicularity

A line drawn through the center of a circle bisecting a chord is perpendicular to the chord.

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Equal Chords and Distance from Center

Equal chords in the same circle (or congruent circles) are equidistant from the center (or centers).

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Equidistant Chords are Equal

Chords equidistant from the center of a circle are equal in length.

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Intersecting Chords and Equal Angles

If two intersecting chords of a circle create equal angles with the diameter passing through their point of intersection, then the chords are equal.

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Distance from a Point to a Line

The length of the perpendicular line from a point to another line is the distance between that point and the other line.

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Proof of Equal Chords and Distance

Equal chords of a circle are equidistant from the center (or centers) because they create congruent triangles.

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Central Angle

The angle formed at the centre of a circle by two radii.

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Inscribed Angle

The angle formed by two chords of a circle that share a common endpoint on the circle.

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Radius

A line segment that connects the center of a circle to a point on the circle's circumference.

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Chord-Arc Relationship

If two chords of a circle are equal, then their corresponding arcs are congruent and conversely, if two arcs are congruent, then their corresponding chords are equal.

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Central Angle-Inscribed Angle Relationship

The angle subtended by an arc at the centre is double the angle subtended by it at any point on the remaining part of the circle.

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Cyclic quadrilateral property

Opposite angles of a cyclic quadrilateral add up to 180 degrees.

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Angle at the center

An angle subtended by an arc at the center of a circle is twice the angle subtended by the same arc at any point on the remaining part of the circle.

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Angle in a semicircle

The angle in a semicircle is always a right angle (90 degrees).

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Cyclic quadrilateral

A quadrilateral is cyclic if all its vertices lie on a single circle.

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Angle bisector quadrilateral

The angle bisectors of the internal angles of any quadrilateral form a cyclic quadrilateral.

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Equilateral triangle

An equilateral triangle has all sides equal and all angles equal to 60 degrees.

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Chord equal to radius

A chord that has the same length as the radius of the circle forms an equilateral triangle with the two radii drawn to its endpoints.

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Opposite angles in a cyclic quadrilateral

In a cyclic quadrilateral, the opposite angles are supplementary (add up to 180 degrees).

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Perpendicular Bisector of a Chord

The perpendicular line segment dropped from the center of a circle to a chord.

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Intersecting Circles Theorem

If two circles intersect at two points, the line joining their centers is the perpendicular bisector of their common chord.

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Equal Chords Intersection Theorem

If two equal chords of a circle intersect inside the circle, the segments of one chord are equal to the corresponding segments of the other chord.

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Equal Chords Angle Theorem

If two equal chords of a circle intersect inside the circle, the line joining the point of intersection to the center makes equal angles with the chords.

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Concentric Circles Theorem

If a line intersects two concentric circles (circles with the same center) at four points, the segments enclosed by the line between the two circles are equal.

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Angle Subtended by an Arc

The angle formed by an arc at the center of a circle is twice the angle formed by the same arc at any point on the circle's circumference.

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Angles in the Same Segment

Angles formed by the same arc in the same segment of a circle are equal.

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Cyclic Quadrilateral Opposite Angles

In a cyclic quadrilateral, the sum of opposite angles is 180 degrees.

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Cyclic Quadrilateral with Diameter Diagonals

If the diagonals of a cyclic quadrilateral are diameters of the circle, the quadrilateral is a rectangle.

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Cyclic Trapezium

A trapezium with equal non-parallel sides is cyclic, meaning all four vertices lie on a circle.

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Angles Opposite Equal Sides

Angles opposite to equal sides in a triangle are equal.

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Angle Sum Property of Triangle

The sum of all angles in a triangle is 180 degrees.

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Study Notes

Circles

  • A circle is a collection of points in a plane that are equidistant from a fixed point called the center.
  • The fixed distance from the center to any point on the circle is called the radius.
  • A line segment joining any two points on the circle is called a chord.
  • A chord passing through the center is called a diameter.
  • The part of a circle between two points on it is called an arc.
  • An arc that forms a semicircle is called a semi-circular arc.
  • Shorter arcs are called minor arcs.
  • Longer arcs are called major arcs.
  • The region enclosed by a chord and a minor arc is called a minor segment, the region enclosed by a chord and a major arc is called a major segment.
  • The area enclosed by an arc and the two radii joining the center to the endpoints of the arc is called a sector.

Equal Chords and Angles

  • Equal chords of a circle subtend equal angles at the center.
  • If the angles subtended by chords at the center are equal, then the chords are equal.
  • Equal chords of a circle (or congruent circles) are equidistant from the center (or centers).
  • The perpendicular from the center of a circle to a chord bisects the chord.
  • The line joining the center of a circle to the midpoint of a chord is perpendicular to the chord.

Theorems

  • Theorem 9.1: Equal chords of a circle subtend equal angles at the center.
  • Theorem 9.2: If the angles subtended by two chords at the center are equal, the chords are equal.
  • Theorem 9.3: The perpendicular from the center of a circle to a chord bisects the chord.
  • Theorem 9.4: The line drawn through the center of a circle to bisect a chord is perpendicular to the chord.
  • Theorem 9.5: Equal chords of a circle (or of congruent circles) are equidistant from the center (or centers).
  • Theorem 9.6: Chords equidistant from the center of a circle are equal in length.

Cyclic Quadrilateral

  • A quadrilateral whose vertices all lie on a circle is called a cyclic quadrilateral.
  • The sum of the opposite angles in a cyclic quadrilateral is 180 degrees.
  • If the sum of the opposite angles of a quadrilateral is 180 degrees, the quadrilateral is cyclic.

Supplementary Angles

  • Angles in the same segment of a circle are equal.

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Explore the fundamental properties of circles and chords in this quiz. Understand concepts like radius, diameter, arcs, and segments, as well as the relationship between equal chords and angles. Perfect for strengthening your geometry knowledge.

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