To begin with, let's understand what a circle is and what is its difference from a circle. Take a pen or pencil in red and draw a regular circle on a piece of paper. Fill the entire middle of the resulting shape with a blue pencil. The red contour denoting the borders 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 the two points so that they are a mirror image of each other. Connect them with a line. A segment will necessarily pass through a point in 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 closes with opposite ends, is called a chord. Therefore, the chord, which runs through the point of the center of the circle, is its diameter.
The diameter is denoted by the Latin letter D. You can find the diameter of the circle by such values as the area, length and radius of the circle.
The distance from the center point to the point laid on the circle is called the radius and is denoted by the letter R. Knowing the radius value helps to calculate the diameter of the circle in one simple step:
D = 2 * R
For example, the radius is 7 cm. We multiply 7 cm by 2 and get a value equal to 14 cm. Answer: D of the given figure is 14 cm.
Sometimes it is necessary to determine the diameter of a circle only by its length. Here you need to apply a special formula to help determine the circumference. 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 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. Suppose the length is 7 m. Therefore:
D = 7/3, 14
D = 21, 98
Answer: the diameter is 21.98 meters.
If the area value is known, then the diameter of the circle can also be determined. The formula that 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 equal to 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 used: D = (6 V / Pi) * 1/3.
Sometimes you have to find the diameter of a circle inscribed in a triangle. To do this, according to 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 obtained is doubled, given that D = 2 * R.
Often it is necessary to find the diameter of the 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 thread. Mark the points of contact between the two ends. Measure the length from point to point with a ruler. We multiply the obtained value by 3.14, following the formula for determining the diameter at a known length. So, the statement that knowledge in geometry and algebra is not useful in life does not always correspond to reality. And this is a serious reason to take a more responsible attitude to school subjects.