• Nisan 10, 2020

# How to Find the Circle Length – Lifehacker ## 1. How to find the circumference through diameter

Just multiply the diameter by the number pi.

• O is the desired circumference.
• π (pi) is a constant equal to 3.14.
• d is the diameter of the circle.

## 2. How to find the circumference through a radius

• O is the desired circumference.
• π (pi) is a constant equal to 3.14.
• r is the radius of the circle.

## 3. How to calculate the circumference through the circle area

Multiply pi by four squares of the circle.

Find the root of the result.

• O is the desired circumference.
• S is the area of ​​the circle. Recall that a circle is a plane inside a circle.
• π (pi) is a constant equal to 3.14.

## 4. How to find the circumference through the diagonal of an inscribed rectangle

Multiply the pi by the diagonal.

• O is the desired circumference.
• π (pi) is a constant equal to 3.14.
• d is any diagonal of the rectangle.

## 5. How to calculate the circumference through the side of the described square

Multiply pi by the side of the square.

• O is the desired circumference.
• π (pi) is a constant equal to 3.14.
• a is either side of the square.

## 6. How to find the circumference through the sides and the area of ​​the inscribed triangle

Multiply the sides of the triangle.

Divide the result by square and two.

Multiply the resulting number by pi.

• O is the desired circumference.
• π (pi) is a constant equal to 3.14.
• S is the area of ​​the triangle.
• a, b, c are the sides of the triangle.

## 7. How to find the circumference through the area and half-perimeter of the described triangle

Divide the area of ​​the triangle by its half-perimeter.

Multiply the result by pi and two.

• O is the desired circumference.
• π (pi) is a constant equal to 3.14.
• S is the area of ​​the triangle.
• p is the semiperimeter of the triangle (equal to half of the sum of all sides).

## 8. How to calculate the circumference through the side of an inscribed regular polygon

Divide 180 degrees by the number of sides of the polygon.

Find the sine of the resulting number.

Divide the side of the polygon by the result.

Multiply the resulting number by pi.

• O is the desired circumference.
• a is the side of a regular polygon. Recall that in a regular polygon all sides are equal.
• π (pi) is a constant equal to 3.14.
• N is the number of sides of the polygon. For example, if a pentagon appears in the problem, as in the image above, N will be 5. 