Checking and securing understanding of interior angles
Lesson details
Learning outcome
I can find the interior angle of any regular polygon or deduce the interior angle of an irregular polygon.
Key learning points
- Any polygon can be split into triangles.
- Using these triangles you can demonstrate the rule for the interior angle sum of a polygon.
- A missing interior angle in any polygon can be found.
- The number of sides in a regular polygon can be determined from the size of the interior angle.
- The sum of the interior angles is the same, regardless of whether the polygon is regular.
Keywords
Polygon - A polygon is a flat (2D), closed figure made up of straight line segments.
Regular - A regular polygon has sides that are all equal and interior (inside) angles that are all equal.
Interior angle - An interior angle is an angle formed inside a polygon by two of its edges.
Common misconception
The size of an interior angle in a regular shape cannot be found unless the size of the other angles are given.
A regular shape has the property that all of its interior angles are equal in size. This means that the size of each interior angle is very easy to find if, for example, the sum of the interior angles is known.
Teacher tip
The second learning cycle focuses on deductive reasoning. Encourage students to discuss the most efficient first step for tackling angle problems.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Angles that meet at a single point on a straight line sum to °.
Q2.Angles are __________ if they sum to 180°.
Q3.Two angles meet to form a straight line. One angle is 60°. The other angle is °.
Q4.Squares and equilateral triangles are examples of __________ polygons.
Q5.A regular octagon has an edge with length 5 cm. Therefore, its perimeter is cm.
Q6.A regular decagon has a perimeter of 40 cm. Therefore, each of its edges are of length cm.
Assessment exit quiz
6 Questions
Q1.Two of the interior angles of a triangle are 80° and 45°. The size of the third interior angle is °.
Q2.The interior angles of a pentagon sum to °.
Q3.Each interior angle of a regular hexagon is °.
Q4.A regular polygon has interior angles of size 150°. The polygon has sides.
Q5.Which of these interior angles are possible in a regular polygon?
Q6.One of the interior angles in an isosceles triangle is 70°. Which are possible sizes for one of the other interior angles?
To help you plan your 10 maths lesson on: Checking and securing understanding of interior angles, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 10 maths lesson on: Checking and securing understanding of interior angles, 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.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 4 maths lessons from the Angles unit, dive into the full secondary maths curriculum, or learn more about lesson planning.