GCSE Maths (AQA)

435 videos | 33 hours

Circle-Tangent Equation

Please subscribe to watch this video.

This, and all other videos, are included in our premium subscriptions.

Premium accounts get access to all videos.

Algebra Graphs

Circle-Tangent Equation

5:25 Graphs of Circles
Spec A16
Previous Equation of a Circle Next Defining Equations
  • The tangent to a circle at a point is perpendicular to the line joining that point to the center of the circle.
  • The equation of the tangent line can be found by drawing a line from the center of the circle to the point where the tangent touches the circle.
  • The equation of the tangent line is y = mx + c, where m is the gradient and c is the y-intercept.
  • The gradient of the tangent line, mp, is equal to -1/m, where m is the gradient of the radius line.
  • To find the equation of the tangent line, substitute the x and y coordinates of a known point on the circle into the equation and solve for m and c.
  • Example: Find the equation of the tangent to the circle x^2 + y^2 = 13 at the point (3, -2). The equation of the tangent is y = 1.5x - 6.5.
  • It is important to practice finding the equation of tangents to circles as it tests knowledge of circle theorems and equations.

Please subscribe to access these revision notes.

This, and all other video notes, are included in our premium subscriptions.

Premium accounts get access to all videos and revision notes.