The equation of a circle

Why x² + y² = r² describes a circle centred at the origin.

Higher

The tangent to a circle at a point

Finding the tangent’s equation from the radius it is perpendicular to.

Higher

Where a line crosses a circle

Substituting the line into the circle’s equation to count the meeting points.

Higher

Practice

The equation of a circle

Why x² + y² = r² describes a circle centred at the origin.

Practice

The tangent to a circle at a point

Finding the tangent’s equation from the radius it is perpendicular to.

Practice

The equation of a circle review

Radius, points on a circle, and tangents at a given point.

Mixed review