Constructing triangles

Measuring the angles and area of a triangle

Special straight lines in a triangle


This first look at triangles during the first two years of secondary education is mainly focused on the following: constructing triangles using a ruler and compass, characteristics of equal triangles, angles and area. Before studying this unit students should be familiar with how to measure angles and carry out operations with them.

Although the study of special lines in a triangle usually takes place during the third and fourth years of secondary education a general introduction to this area in the second year is useful, and the Nippe Descartes programme is an excellent way of doing this.

  • To learn different ways of constructing triangles using a ruler and compass. 
  • To introduce the concept of using geometric representation to work out the sum of the angles in a triangle and its area.
  • To work out the size of the angles and area of any triangle.
  • To be familiar with and construct various lines in a triangle such as the perpendicular bisector, angle bisector and median as well as knowing how to find the point where these lines intersect.

  Miguel García Reyes
Spanish Ministry of Education. Year 2001

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