JHS3 Mathematics · Term 2, Week 11
Shapes and Space
Lesson notes
Learning Objectives
Indicator: B9.3.1.2.1 - Draw inscribed and circumscribed circles for triangles under given conditions
By the end of the lesson, learners can:
- Construct a triangle under a given condition using a pair of compasses and a ruler, and bisect any two of its angles accurately.
- Locate the incentre of a triangle as the intersection of two angle bisectors and state the relationship between the incentre and the three sides of the triangle.
- Construct an inscribed circle (incircle) that touches all three sides of a given triangle and verify by measuring the perpendicular distances from the incentre to each side.
- Bisect any two sides of a triangle with perpendicular bisectors and locate the circumcentre as their intersection.
- Construct a circumscribed circle (circumcircle) that passes through all three vertices of a given triangle and verify by measuring the distances from the circumcentre to each vertex.
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Sign in with phone numberCurriculum details
- Strand
- Geometry and Measurement (Strand 3)
- Sub-strand
- Shapes and Space (3.1)
- Content standard
- B9.3.1.2 - Construct inscribed and circumscribed triangles and parallelograms with given dimensions.
- Indicator
- B9.3.1.2.1 - Draw inscribed and circumscribed circles for triangles under given conditions
- Suggested placement
-
Term 2, Week 11
(Week 23 of the year)
Our suggestion, laid out in curriculum order across three terms of twelve weeks. NaCCA does not fix the week, so follow your school's scheme of learning.
- Curriculum reference
-
Mathematics, Common Core Programme (JHS1-JHS3), 2023, p. 199
Transcribed from the official NaCCA publication. Check this page against the source.
Exemplars (from the NaCCA curriculum)
E.g.1: Use a pair of compasses and a ruler to construct a triangle (say ∆ABC) under a given condition and locate the incentre of the triangle (the incentre is the point of concurrency of the three angle bisectors of a triangle); measure the shortest distance from the incentre to the line segments AB, AC and BC. What do you observe about the lengths?
E.g..2: Use a pair of compasses and a ruler to construct a triangle (say ABC) under a given condition, bisect at least any two angles (∆BAC and ∆BCA); locate the intersection of the two angle bisectors (L) and draw a locus of points equidistant from the fixed point (L) to touch the edges of the triangle.
E.g.3: Construct a triangle (say ABC); bisect all three sides (i.e. line segments AB, AC and BC); locate the intersection (circumcentre) of the three perpendicular bisectors (S); Measure the distance from the intersecting centre (S) to points A, B and C. What do you observe about the lengths?
E.g.4: Perform a geometric construction of a triangle (say ABC) under a given condition; bisect at least any two sides (AB and BC); locate the intersection of the two perpendicular bisectors (O) and draw a locus of points equidistant from the fixed point (O) to circumscribe the triangle.