Let's talk about what the ruler and protractor are for. These two useful tools are used not only at school in geometry and drawing lessons, but also in everyday life.
The purpose of the ruler
A ruler is a long narrow rectangular strip with a scale and numbers plotted on the upper edge (on some rulers and on the bottom).
What is a human ruler for? Firstly, for measuring small distances, lengths, heights and widths of various objects; secondly, for drawing straight straight lines with a pencil, pen, felt-tip pen. That is, the line has two main functions: measuring and drawing straight lines. Both are often used at once, for example, you need to draw a rectangle with sides of 5 cm and 7 cm. We take a ruler, put it on the sheet in the right place first horizontally, draw from 0 to 7 cm with a pencil, then draw perpendicular sides at the ends of 5 cm and finish the top side 7 cm.
On the other hand, the ruler is not used for constructions, but simply for measurements. For example, you need to measure the length of a pen to see if it fits in a miniature pencil box or not.
Appointment of the protractor
Now let's talk about the appointment of a protractor, how to use it. In geometry and drawing, you often have to build lines at a certain angle. Without a tool, only three angles can be distinguished: 0 ° - horizontal, 90 ° - vertical, 180 ° - adjacent (also horizontal, but on the other side from 0 °.
Above we figured out what the ruler is for. A protractor is also a useful and necessary item, but is used very rarely in everyday life. In construction, for example, it is replaced by a level.
To build an angle, for example, 75 ° , you should attach the protractor to the desired line so that the upper part of its horizontal ruler lies on the drawn line. Then on the scale of the protractor we find 75 about . We put a point near the mark "75", as well as the second point in the center of the protractor line. That's it, connect the two points and get a line at an angle of 75 about . That's why you need a ruler with a hole or mark in the center opposite to 90 ° on each protractor.
Where else are used
Very often when carrying out repairs, compiling tables in magazines and notebooks, creating various products by masters of various professions, housewives, workers, this tool is used. What is a ruler for, for example, for an accountant? When entering data from sheets into a computer, it imposes a ruler on the line with which you need to work. So he will not lose the place where he stopped.
These are the useful properties of the ruler and protractor! But they are inexpensive and accessible to everyone.