A selection of free mathematics resources (calculators, exercises, games, quizzes, course reminders) to learn geometry.

The **perimeter of a closed figure** is defined as the length of its contour.

The **formula for calculating the perimeter of a circle is `P=2*pi*r`**, where r is the radius of the circle.

Example : the perimeter of a circle of length 1 is equal to 2*pi.

The **perimeter of a rectangle is given by the formula `2*(L+l)`** where L represents the length and l the width of a side.
Applying this formula, it is possible to verify that the
perimeter of a rectangle of length is 3 and width is 2 is equal to 10
.

The **perimeter of a square is given by the formula `4*a`** where a is the length of one side of the square.
Using this formula, we can show that the
perimeter of a square of length 2 equals 8
.

The **perimeter of a triangle is given by the formula a+b+c**
where a, b, and c represent the length of each side of the triangle.
Using this formula, we can see that the
perimeter of a triangle whose sides have lengths 5, 6, 7 is equal to 18
.

The ** area of a circle is given by the formula `pi*r^2`**, where r represents the radius of the circle.

By applying this formula, it is possible to find the area of a circle of radius 3 .

The ** area of a rectangle is equal to the product of its sides, it is calculated with the formula `(L*l)`**, where L represents the length and l the width of a side.
Using this formula, we can verify that the
length is 3 and the width is equal to 6
.

The ** area of a square is given by the formula `a^2`** where a represents the length of one side of the square.

Using this formula, we can, for example, calculate the area of a square whose side length is 3.

The **area of a triangle can be calculated using Heron's formula
, which is written: `S=sqrt(p*(p-a)*(p-b)*(p-c)`**, where a, b, c represent the length of the sides of the triangle, and p is the half perimeter `p=(a+b+c)/2`.

Using this formula, we can, for example, calculate the area of a triangle of a triangle where the length of each of the sides would be 3, 4, and 5 respectively.

The **volume of a sphere is given by the formula `4/3*pi*r^3`**, where r represents the radius of the sphere.
For example, this formula can be used to
calculate the volume of a sphere of radius 3.

The **volume of a rectangular parallelepiped is given by the formula `(L*l*h)`**,
where L represents the length, l the width of a side, and h the height.
Using this formula, we can
calculate the volume of a rectangular parallelepiped whose length is 3, width is 2, and height is 4
.

The **volume of a cube is given by the formula `l^3`**, where l is the length of a side.
By applying this formula, it is possible to
find the volume of a cube that has sides of length 3
.

The **Pythagorean theorem** is stated as follows :
In a right triangle, the square of the hypotenuse is equal to the sum of the squares of the opposite sides.
If we consider the triangle ABC rectangular in A, if we pose BC=a, AC=b, AB=c then the Pythagorean theorem is written
`BC^2=AB^2+AC^2` or `a^2=b^2+c^2`.

The **Pythagorean theorem admits a reciprocal** which states: If in a triangle the square of one side is equal to the sum of the squares of the opposite sides, then the triangle is rectangular.

By applying the Pythagorean theorem, it is for example possible to calculate the length of the hypotenuse of a right-angled triangle whose adjacent sides have lengths of 3 and 4 .

- area : Calculation of the area of a geometric figure.. Online area calculator which allows to calculate the area of a rectangle, square, triangle or circle.
- area_circle : area of a circle. area online calculator that can calculate the area of a circle from its radius or from its diameter.
- area_rectangle : area of a rectangle. area online calculator that can calculate the area of a rectangle from its length and its width.
- area_square : area of a square. area online calculator that can calculate the area of a square from the length of a side.
- equation_straight_line : find equation of a straight line from two points. The equation straight line calculator allows to calculate the equation of a straight line from the coordinates of two points with step by step calculation.
- perimeter : perimeter calculator. Online perimeter calculator that calculates rectangle perimeter, square perimeter, triangle perimeter or circle perimeter.
- perimeter_circle : perimeter of a circle. Online calculator that calculates the perimeter of a circle from its radius.
- perimeter_rectangle : perimeter of a rectangle. The online calculator allows to calculate the perimeter of a rectangle from its length and its width.
- perimeter_square : perimeter of a square. The online calculator allows to calculate the perimeter of a square from the length of a side.
- pythagorean : Pythagorean theorem calculator. The calculator uses the Pythagorean theorem to verify that a triangle is right-angled or to find the length of one side of a right-angled triangle.
- volume_cube : volume of a cube. The online calculator allows to calculate the volume of a cube from the length of a side.
- volume_rectangle : volume of a rectangular parallelepiped. The online calculator allows to calculate the volume of a rectangle from its length, its width and height.
- volume_sphere : volume of a sphere. The online calculator allows to calculate the volume of a sphere from its radius.

- game about area calculations of usual figures. (geometry): This game allows you to practice the calculation of simple surfaces: square, rectangle, circle.
- perimeter game (geometry): This game allows you to practice calculating perimeters on common shapes: square, rectangle, triangle, circle.

- Exercise 1242, calculation of the perimeter of a circle - perimeters and areas : The purpose of this exercise is to calculate the perimeter of a circle knowing its radius.
- Exercise 1245, calculating the area of a disk - perimeters and areas : The purpose of this corrected exercise is to practice calculating the area of a disk.
- Exercise 3300, calculate the hypotenuse of a right triangle - right-angled triangles : The purpose of this exercise is to calculate the hypotenuse of a right triangle using the Pythagorean theorem.
- Exercise 3441, coordinates of a vector from the coordinates of two points - vectors : The purpose of this corrected exercise is to calculate the coordinates of a vector from the coordinates of two points.
- Exercise 3442, calculation of the distance between two points - vectors : The purpose of this corrected exercise is to calculate the distance between two points from their coordinates.
- Exercise 3443, calculation of the coordinates of the middle of a segment - vectors : The purpose of this corrected analytical geometry exercise is to calculate the coordinates of the midpoint of a segment from coordinates.
- Exercise 11201, calculation of the area of a rectangle - perimeters and areas : The purpose of this corrected exercise is to practice calculating the area of a rectangle.
- Exercise 11202, calculating the area of a square - perimeters and areas : The purpose of this corrected exercise is to practice calculating the area of a square.
- Exercise 11203, calculation of the perimeter of a rectangle - perimeters and areas : The objective of this exercise is to calculate the perimeter of a rectangle knowing its length and width.
- Exercise 11204, calculating the perimeter of a square - perimeters and areas : The objective of this corrected exercise is training in calculating the perimeter of a square knowing the length of a side.

Algebraic calculation | Equations | Finance | Real functions | Trigonometric functions | Fractions | Geometry | Matrices | Numbers | Complex numbers | Statistics | Numerical sequences | Time | Vectors