Circle Lab
Arcs, angles, chords and tangents, drawn from real numbers.
Circle Lab covers the circle unit of a high school geometry course. It begins with the parts of a circle, such as the radius, diameter, chord, secant, tangent, arc, sector and segment. Then it turns to central angles and arcs, and to inscribed angles, including the angle in a semicircle and angles in an inscribed quadrilateral.
Students go on to angles formed by chords, secants and tangents, segment lengths where two chords or two secants cross, arc length and sector area, and finally the equation of a circle on a grid. Every picture is drawn from the real numbers, so a drawn diameter passes through the center and a tangent touches the circle at one point.
What children practice
- Name the radius, diameter, chord, secant, tangent, arc, sector and segment
- Find arc measures from central angles, and major and minor arcs
- Use the inscribed angle theorem and the angle in a semicircle
- Find angles and lengths made by chords, secants and tangents
- Calculate arc length and sector area, in terms of pi or rounded as stated
- Write and read the equation of a circle from its center and radius
Levels
- Level 1: Parts of a circle
- Level 2: Central angles and arcs
- Level 3: Inscribed angles
- Level 4: Chords, secants, tangents
- Level 5: Segment lengths
- Level 6: Arc length and sectors
- Level 7: Equation of a circle
- Level 8: Course mix
How it works
- Eight levels go from the parts of a circle to its equation, and the last level mixes everything, including some two-step rounds.
- Diagrams are drawn from the question's numbers, with angle marks sitting between the rays they describe.
- A level unlocks when your child has five correct answers and the practice timer has run out.
- Questions use choices, typed answers, tapping parts of a figure, sorting and ordering steps.
Best for: A good fit for grades 10 to 11 when a geometry class reaches circles, or when a student needs to see why the circle theorems are true.
Tip for parents: Draw a circle with a compass and ask your child to mark a diameter, then pick a point on the circle and join it to both ends. Measuring that angle shows the semicircle rule in action.
Questions parents ask
Are answers given in terms of pi?
Level 6 does both. Some questions ask for an answer such as 12 pi, while others ask for a rounded value, and the question says which one, using 3.14 for pi when rounding.
Does the game include the equation of a circle?
Yes. Level 7 asks for the center and radius, whether a point is inside, on or outside the circle, and completing the square to reach the standard form.
Why do the pictures matter?
Because they are drawn from the same numbers as the question, students can trust what they see. Equal tangents look equal and a radius meets a tangent at a right angle.
Ready to try it?
Circle Lab is free with a parent account. A parent adds a child profile, and the child's progress is saved.