Calculating arc length
I can calculate the arc length of a sector and the sector's perimeter.
Calculating arc length
I can calculate the arc length of a sector and the sector's perimeter.
These resources will be removed by end of Summer Term 2025.
Lesson details
Key learning points
- Using fractions, you can calculate part of the circumference.
- This gives the length of the curved section of a sector.
- To find the perimeter, you will need to add the radius twice.
- An exact answer may be given in terms of π
Keywords
Arc - An arc is part of a curve. An arc of a circle is part of the circle’s circumference.
Sector - A sector is the region formed between two radii and their connecting arc.
Chord - A chord is any line segment joining two points on the circumference of a circle.
Radius - The radius is any line segment that joins the centre of a circle to any point on its circumference.
Circumference - The circumference of a circle is the perimeter of the circle.
Common misconception
"When finding the perimeter of a sector, I need to multiply the radius by a fraction of a full circle, just like I did with the circumference to find the arc length."
Reminder that only part (the arc length) of the formula for perimeter of a sector varies with the angle. A desmos or geogebra model can help to show this.
To help you plan your year 10 maths lesson on: Calculating arc length, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your year 10 maths lesson on: Calculating arc length, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
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The assessment exit quiz will test your pupils' understanding of the key learning points.
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Explore more key stage 4 maths lessons from the 2D and 3D shape: compound shapes unit, dive into the full secondary maths curriculum, or learn more about lesson planning.
Licence
Starter quiz
6 Questions




Exit quiz
6 Questions




