How to find a circle radius

Often, when a schoolboy gives proms at school or introductory to any university, it needs certain knowledge in the field of geometry. Moreover, the tasks are not so complex, just need to remember the basic formulas to apply them in the decision. The tasks in which it is necessary to find a circle radius is not an exception. In principle, they are quite simple in solving. In this article we will tell you how to find a circle radius in different ways.

1

We find the radius of the circle, based on the formulas

When you get a task on the control or on the exam in which you need to find a circle radius, first of all it is necessary to analyze the available data. Because it is from them that will depend on the decision of the decision in general. For example, you can find the amount under consideration using such parameters: the length of the circle, its area, diameter, etc. We will consider the simplest and most common ways to solve problems in which the circle radius is unknown.

We all know that the radius of the circle is the length of its center to any point, which is located on the circumference itself. In this regard, solutions may be as follows:

1. When you in the source data of the task, the circle diameter is given, the solution here will be simpler simple. After all, we know that the diameter is a segment that connects several points on the circle, passing through its center. It follows from this that the diameter is 2 radius. Then we find the radius by the formula: R \u003d D / 2, where R is the radius of the circle, and D, respectively, its diameter. For example, the diameter by condition is 32 cm, then the radius we calculate this: 32/2 \u003d 16 cm.
2. Go to the next way to solve. Suppose you are in the condition given the length of the circle. I am expressed by the mathematical language, this is the so-called perimeter. We know perfectly well that there is a special formula for finding the circumference length: p \u003d 2πr. Hence, we can derive the radius formula: R \u003d p / 2π. Now consider this on the example. Suppose, according to the condition of the problem, the circumference is given to you, equal to 31.4 cm, and π in mathematics - the value is constant and always equal to 3.14; Then the radius find as follows: 31.4 / 2 * 3,14 \u003d 5 cm.
3. Now consider how to find the radius of the circle, if its area is given. The formula of the area of \u200b\u200bthe circle has this kind: S \u003d πr2. From here we find the radius formula: R \u003d √ (S / π). Again, consider everything in digital calculus. Let you be given in the condition of the task of the area, for example - 28.26 cm2. We substitute the data in the formula we derived and obtain: √28.26 / 3.14 \u003d 3 cm.

Now you will not be difficult to solve any task with finding the radius of the circle. The main thing is to clearly analyze the source data, and then apply the appropriate formula, and you can consider yourself a great mathematician.