Tangents to a Circle (GMAT/GRE/CAT/Bank PO/SSC CGL) | Don't Memorise | Summary and Q&A

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June 1, 2015
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Tangents to a Circle (GMAT/GRE/CAT/Bank PO/SSC CGL) | Don't Memorise

TL;DR

Tangents and circles intersect in three ways - not at all, at one point, or at two points - and the length of an arc can be calculated using the central angle and the circumference.

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Key Insights

  • 🔵 Tangents to a circle can meet the circle at zero, one, or two points, and are called tangents and secants respectively.
  • 🔺 The radius to the point where a circle and tangent meet will always be perpendicular to the tangent.
  • 🛡️ Two tangents drawn from an external point to a circle will be equal in length.
  • 🎯 Tangent lengths can be found using the concept of radii perpendicular to the tangents and angles of a quadrilateral.
  • ⭕ The length of an arc on a circle depends on its central angle and the circle's circumference.
  • 📐 The measure of angle AOB can be found by using the angles of the quadrilateral formed by the tangents and radii.
  • ➰ The length of Arc ACB can be calculated using the central angle of 120 degrees and the circle's circumference of 12 centimeters, resulting in a length of 4 centimeters.
  • 🔢 Competitive exams may test multiple concepts, requiring the application of various formulas and principles simultaneously.

Transcript

in how many ways can a circle and a straight line lie on a plane one way would be like this where they don't meet at all another way is like this where they meet at exactly one point such lines are called tangents a line which meets a circle at exactly one point is called the tangent and the third way in which it can meet the circle is like this at... Read More

Questions & Answers

Q: How can tangents intersect circles and what are their properties?

Tangents can intersect circles in three ways: not at all, at one point (tangent), or at two points (secant). When a circle and a tangent meet, the radius to the point of intersection is always perpendicular to the tangent.

Q: What is the significance of drawing tangents from an external point to a circle?

When drawing tangents from an external point to a circle, the lengths of the tangents will be equal. Additionally, the radii drawn to the points of tangent intersection are perpendicular to their respective tangents.

Q: How can the length of an arc be calculated?

The length of an arc depends on the central angle it subtends and the circumference of the circle. By using the formula (central angle/360 degrees) x circumference, the length of the arc can be determined.

Q: How can the measure of a central angle be determined?

The measure of a central angle can be determined by considering the properties of a quadrilateral formed by the tangents and radii. By using the sum of the angles in the quadrilateral (360 degrees), the measure of the central angle can be calculated.

Summary & Key Takeaways

  • Tangents can intersect circles in three ways: not at all, at one point (tangent), or at two points (secant).

  • The radius to the point where the circle and the tangent meet is always perpendicular to the tangent.

  • When drawing tangents from an external point to a circle, the lengths of the tangents will be equal.

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