If each side has a parallel opposite side (two pairs of parallel sides), the shape can be called a parallelogram. Parallelograms: One property that quadrilaterals can have is that they can have parallel opposite sides. There are even more named varieties of quadrilaterals than there are varieties of triangles.
Polygons that have 4 sides are quadrilaterals. In the Montessori work, they use the exclusive definition for isosceles, so the grid looks like this: The children trace the triangles into the grid. The Montessori "7-triangles of reality" work involves sorting the triangles in both ways simultaneously into a grid. I wonder which definition you'll find at your school?Įach triangle can be sorted both by their side lengths and by their angle measures Isosceles sometimes means that at least two of the side lengths are the same, and it sometimes means that exactly two of the side lengths are the same: there's an inclusive and an exclusive version of the definition. Scalene always means that all of the side lengths are different.Įquilateral always means that all of the side lengths are the same. There are two different ways you might find triangles classified: Triangles can be classified by how many sides are congruent.
Triangles can be classified by angle size into acute triangles, right triangle and obtuse trianglesĪn acute triangle is a triangle where all of the angles are acute.Īn acute triangle is a triangle where the largest angle is acuteĪ right triangle is a triangle where one of the angles is a right angle.Ī right triangle is a triangle where the largest angle is a right angleĪn obtuse triangle is a triangle where one of the angles is obtuse.Īn obtuse triangle is a triangle where the largest angle is obtuse Hopefully, these are all terms that you knew before, and I'm just reminding you and refreshing your memory. Properties of triangles and quadrilaterals Lesson 7.5: Standard definitions of special polygons