For starters, let's figure out what a circle is and how it differs from a circle. Take a red pen or pencil and draw a regular circle on a piece of paper. Paint over the entire middle of the resulting figure with a blue pencil. The red outline denoting the boundaries of the figure is a circle. But the blue content inside it is the circle.
The dimensions of a circle and a circle are determined by the diameter. On the red line representing the circle, mark two points so that they are mirror images of each other. Connect them with a line. The segment must pass through the point at the center of the circle. This segment, connecting the opposite parts of the circle, is called the diameter in geometry.
A segment that does not extend through the center of the circle, but joins it at opposite ends, is called a chord. Therefore, the chord passing through the center point of the circle is its diameter.
The diameter is denoted by the Latin letter D. You can find the diameter of a circle by such values as the area, length and radius of the circle.
The distance from the center point to the point plotted on the circle is called the radius and is denoted by the letter R. Knowing the value of the radius helps to calculate the diameter of the circle in one simple step:
D=2R
For example, the radius is 7 cm. Multiply 7 cm by 2 and get a value equal to 14 cm. Answer: The D of the given figure is 14 cm.
Sometimes you have to determine the diameter of a circle only by its length. Here it is necessary to apply a special formula to help determine the circumference of a circle. The formula L=2 PiR, where 2 is a constant value (constant), and Pi=3, 14. And since it is known that R=D2, the formula can be represented in another way
L=PiD
D=L / Pi
This expression is also applicable as a formula for the diameter of a circle. Substituting the known values in the problem, we solve the equation with one unknown. Let's say the length is 7 m. Therefore:
D=7 / 3, 14
D=21, 98
Answer: the diameter is 21.98 meters.
If you know the value of the area, you can also determine the diameter of the circle. The formula that applies in this case looks like this:
D=2(S / Pi)(1 / 2)
S - in this case, the area of the figure. Let's say in the problem it is 30 square meters. m. We get:
D=2(30 / 3, 14)(1 / 2) D=9, 55414
When the value indicated in the problem is equal to the volume (V) of the ball, the following formula for finding the diameter is applied: D=(6 V / Pi)1 / 3.
Sometimes you have to find the diameter of a circle,inscribed in a triangle. To do this, by the formula we find the radius of the presented circle:
R=S / p (S is the area of the given triangle and p is the perimeter divided by 2).
The result is doubled, given that D=2R.
It is often necessary to find the diameter of a circle in everyday life. For example, when determining the size of a ring, which is equivalent to its diameter. To do this, wrap the finger of the potential owner of the ring with a thread. Mark the points of contact between the two ends. Measure the length from point to point with a ruler. The resulting value is multiplied by 3, 14, following the formula for determining the diameter with a known length. So, the statement that knowledge in geometry and algebra will not be useful in life does not always correspond to reality. And this is a serious reason to treat school subjects more responsibly.
