How to measure the diameter of the circle, if you do not have the necessary tools for this at hand? In fact, it is quite simple.

To do so, use the method described below.

You will need

- - Subject whose diameter is to be calculated.
- - Pencil or marker.
- - The ruler or tape measure.
- - A sheet of paper, cardboard or plywood rectangular shape and of suitable size (see figure to step 2.).

instructions

1

According to the theorem of the inscribed triangle ofschool geometry course, we know that the right-angled triangle can be inscribed in any circle, as well as to describe a circle around the right-angled triangle whose vertices lie on its arc.

2

Using this knowledge, take both subjects: one that has a circular shape and a rectangular sheet of paper, cardboard or other material. Moreover, the angles in a rectangular object should not be rounded, it will fairly precisely measure **diameter** circumference. Size of the rectangular object has to be such that its two opposite sides intersect the circle at two points.

3

According to the same theorem, the hypotenuse (side of the triangle opposite the right angle) of a right triangle is equal to **diameter**have described a circle around it. To do this, take a sheet of cardboard or other rectangular object, and impose it on the circle so that the right angle? And its tip rested in the arc of a circle as shown below.

4

Mark with a pencil or a marker of the points at which the rectangle intersects the circle. The figure they are marked as points E and F. Connect points E and F by a straight line. This segment EF is **diameter** Our circle. Measure its simple ruler or tape measure. The diameter of the circle is calculated.