To begin with, let's figure out what isand what is its difference from the circle. Take a pen or pencil of red color and draw a regular circle on a piece of paper. Paint the entire middle of the figure with a blue pencil. The red outline that represents the border of the figure is the circle. But the blue content inside it is a circle.
Размеры круга и окружности определяются диаметром.On the red line denoting the circle, mark two points so that they are a mirror image of each other. Connect them with a line. The segment must pass through a point in the center of the circle. This segment, which connects the opposite parts of the circle, is called in geometry by diameter.
A segment that does not extend through the centercircle, but it joins with its opposite ends, is called a chord. Consequently, the chord that passes through the point of the center of the circle is its diameter.
Расстояние от центральной точки до точки, laid out on a circle, is called the radius and is denoted by the letter R. Knowing the radius value helps to calculate the diameter of a circle by one simple action:
D = 2 * R
For example, the radius is 7 cm. Multiply 7 cm by 2 and get a value of 14 cm. Answer: D of the given figure is 14 cm.
Иногда приходится определять диаметр окружности only along its length. Here it is necessary to apply a special formula that helps determine the length of the circle. The formula L = 2 Pi * R, where 2 is a constant value (constant), and Pi = 3.14. And since it is known that R = D * 2, the formula can also be represented in another way
L = Pi * D
D = L / Pi
This expression is also applicable as a formula for the diameter of a circle. Substituting the quantities known in the problem, we solve the equation with one unknown. Let's say the length is 7 m. Hence:
D = 7/3, 14
D = 21, 98
Answer: the diameter is 21.98 meters.
If the value of the area is known, it is also possible to determine the diameter of the circle. The formula, which is used in this case, looks like this:
D = 2 * (S / Pi) * (1/2)
S - in this case the area of the figure. Suppose, in the problem, it is 30 sq. M. 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 used: D = (6 V / Pi) * 1/3.
Sometimes it is necessary to find the diameter of a circle inscribed in a triangle. For this, from the formula, we find the radius of the circumscribed circle:
R = S / p (S is the area of the given triangle, and p is the perimeter divided by 2).
The result is doubled, taking into account that D = 2 * R.
Нередко находить диаметр окружности приходится и at home. For example, when determining the size of a ring, which is equivalent to its diameter. To do this, you need to wrap the finger of the potential ring owner with a thread. Mark the points of contact of 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 for a known length. So, the statement that knowledge in geometry and algebra in life is not useful, does not always correspond to reality. And this is a serious reason to take a more responsible attitude to school subjects.
