Geometry of Circles - Review Set 21

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Questions and Answers

What is the value of x if 56 + x = 142?

x = 86

Using Pythagoras' theorem, what is the radius OB if BM = 5 cm and OB = OA = x?

x ≈ 5.83

How do you express the relationship between obtuse BOD and angle BAD?

obtuse BOD = 2 × BAD = 2α°

What value do you get for angle AOC if AOC + 250° = 360°?

<p><strong>AOC</strong> = 110°</p> Signup and view all the answers

In triangle AOC, if the angles are x, x, and 70°, what is the value of x?

<p>x = 55°</p> Signup and view all the answers

Given the equation 4x + 36 = 180, what is the value of x?

<p>x = 36</p> Signup and view all the answers

If y - 22 + y + 34 + y = 180, what is the value of y?

<p>y = 56</p> Signup and view all the answers

What is the approximate diameter FD of the circle if sin 56° = 5.5 / FD?

<p>FD ≈ 6.63 m</p> Signup and view all the answers

What is the value of angle BOC when BAC is 36°?

<p>72°</p> Signup and view all the answers

If angles ABC, ABO, and AOB form a triangle and ABC is a right angle, what is the value of angle AOB if angle ABC is 90°?

<p>90°</p> Signup and view all the answers

Given that ACD and ABD are angles on the same arc, what is their common value?

<p>41°</p> Signup and view all the answers

In triangle ABC, if the two angles are expressed as x and x + 14, what is the value of x?

<p>38°</p> Signup and view all the answers

What is the relationship between angle ABC and angle AOC given that AOC measures 120°?

<p>ABC = 60°</p> Signup and view all the answers

If angles CAB and CBA are both 38°, what is the value of x in triangle AABC?

<p>104°</p> Signup and view all the answers

In triangle ABC, if angles ACB and ABC satisfy the equation α + β = 90°, what does this imply about triangle ABC?

<p>It is a right triangle.</p> Signup and view all the answers

What relationship can be established between angles AOB and ACB through the circle?

<p>AOB = 2 × ACB.</p> Signup and view all the answers

Flashcards

Angle at the center

The angle formed by two radii of a circle that meet at the center of the circle.

Angle in a semi-circle

The angle formed by two points on the circumference of a semicircle and the endpoints of the diameter is always 90 degrees.

Angles on same arc

Angles subtended by the same arc at the circumference of a circle are equal.

Angle between tangent and chord

The angle formed between a tangent to a circle and a chord drawn from the point of contact is equal to the angle subtended by the chord in the alternate segment.

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Tangents from an external point

The lengths of tangents drawn from an external point to a circle are equal.

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Angles in a triangle

The sum of the angles in any triangle is 180 degrees.

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Isosceles triangle

A triangle with two sides of equal length.

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Alternate angles

Angles that are on opposite sides of the transversal and between the two parallel lines.

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Angle on the Same Arc

Angles subtended by the same arc at the circumference of a circle are equal.

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Radius-Tangent Theorem

A tangent to a circle is perpendicular to the radius drawn to the point of contact.

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Pythagorean Theorem

In a right triangle, the square of the hypotenuse (the longest side) is equal to the sum of the squares of the other two sides.

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Exterior Angle of a Triangle

The exterior angle of a triangle is equal to the sum of the two opposite interior angles.

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Base Angles of Isosceles Triangle

The angles opposite the two equal sides in an isosceles triangle are equal.

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Chord of a Circle

A line segment that connects two points on the circumference of a circle.

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Study Notes

Review Set 21 - Geometry of Circles

  • Angle at the Centre: The angle at the centre of a circle is twice the angle at the circumference subtended by the same arc.
  • Isosceles Triangles: In a circle, if two radii are equal, the triangle formed by connecting the centre and the endpoints of the radii is isosceles. Base angles of an isosceles triangle are equal.
  • Angles in a Triangle: The sum of the angles in any triangle is 180 degrees.
  • Angles in a Semi-Circle: An angle in a semi-circle is a right angle (90 degrees).
  • Tangent and Chord: The angle between a tangent and a chord drawn from the point of tangency is equal to the angle subtended by the chord in the alternate segment.
  • Tangents from an External Point: Tangents drawn from an external point to a circle are equal in length.
  • Midpoint of a Chord: The perpendicular bisector of a chord passes through the centre of the circle.

Practice Test 21B

  • Angles on Same Arc: Angles subtended by the same arc at the circumference are equal
  • Exterior Angle of a Triangle: The exterior angle of a triangle is equal to the sum of the two opposite interior angles.
  • Pythagorean Theorem: In a right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides. a² + b² = c².
  • Radii: Radii of a circle are all equal in length.

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