This is a very fundamental topic which deals with the dimensions of figures. Dimensions in mathematics are nothing but the measure of the distance or size of a region or an object in space in a specified direction. Simply, it can also be denoted as the measurement of the length, width, and height of anything.
The RD Sharma Solutions for Class 7 Maths Chapter 19 visualising solid shapes contains topics like types of dimensions. Dimensions are majorly classified into three types. They are One Dimension, Two Dimension, and Three Dimension. They are also represented as 1D, 2D, and 3D, respectively.
One dimensional figure contains a line segment drawn on a surface and is considered a one-dimensional object because it has only length and no width. Similarly, two-dimensional shapes or objects in geometry are flat plane figures with two dimensions, i.e., length and width. Likewise, three-dimensional shapes are the shapes that are solid figures or objects that have three dimensions to them. Therefore, it has length, height, and width.
Students also study concepts like faces, edges, and vertices of different types of figures. For example, the figures include cube, sphere, cuboid, cone, cylinder, pyramid, etc. Here, students understand how the dimension concepts are being implemented in those shapes. Other than this, nets for building 3D shapes are also taught to students. A net is nothing but a flattened out three-dimensional solid, which looks like a skeleton outline in two dimensions, but when folded and glued together, it obtains a 3D structure. These are used to make 3D shapes.
At last, an important formula is being discussed, which is Euler's formula which is a very important one in maths and engineering. Euler's formula creates a fundamental relationship between the faces, edges and vertices of a 3-D shape.