Planes of symmetry and sections
Count planes of symmetry of solids, find axial sections of cylinder and cone, and use 3-D coordinates for the space diagonal.
- France: grade 2
- Germany: grade 8
- Syria: grade 3
- Palestine: grade 2
- Ukraine: grade 4
Guide
A Symmetrieebene splits a solid into two mirror-image halves. A cuboid with three different edges has 3 of them, a cube 9, a cylinder infinitely many (every plane through its axis, and the middle plane).
The Axialschnitt of a rotation solid is its cut through the axis: a rectangle for the cylinder, an isosceles triangle for the cone, a circle for the sphere.
In the 3-D coordinate system a point has three coordinates P(x₁|x₂|x₃). The Raumdiagonale of a cuboid is √(a² + b² + c²).