# Resources tagged with: Regular polygons and circles

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There are 68 NRICH Mathematical resources connected to Regular polygons and circles, you may find related items under Angles, Polygons, and Geometrical Proof.

Broad Topics > Angles, Polygons, and Geometrical Proof > Regular polygons and circles ### Curvy Areas

##### Age 14 to 16Challenge Level

Have a go at creating these images based on circles. What do you notice about the areas of the different sections? ### Partly Circles

##### Age 14 to 16Challenge Level

What is the same and what is different about these circle questions? What connections can you make? ### Spokes

##### Age 16 to 18Challenge Level

Draw three equal line segments in a unit circle to divide the circle into four parts of equal area. ### Salinon

##### Age 14 to 16Challenge Level

This shape comprises four semi-circles. What is the relationship between the area of the shaded region and the area of the circle on AB as diameter? ### Semi-detached

##### Age 14 to 16Challenge Level

A square of area 40 square cms is inscribed in a semicircle. Find the area of the square that could be inscribed in a circle of the same radius. ### Approximating Pi

##### Age 14 to 18Challenge Level

By inscribing a circle in a square and then a square in a circle find an approximation to pi. By using a hexagon, can you improve on the approximation? ##### Age 14 to 16Challenge Level

Given a square ABCD of sides 10 cm, and using the corners as centres, construct four quadrants with radius 10 cm each inside the square. The four arcs intersect at P, Q, R and S. Find the. . . . ### Orthogonal Circle

##### Age 16 to 18Challenge Level

Given any three non intersecting circles in the plane find another circle or straight line which cuts all three circles orthogonally. ### So Big

##### Age 16 to 18Challenge Level

One side of a triangle is divided into segments of length a and b by the inscribed circle, with radius r. Prove that the area is: abr(a+b)/ab-r^2 ### Logosquares

##### Age 16 to 18Challenge Level

Ten squares form regular rings either with adjacent or opposite vertices touching. Calculate the inner and outer radii of the rings that surround the squares. ##### Age 16 to 18Challenge Level

A circle is inscribed in an equilateral triangle. Smaller circles touch it and the sides of the triangle, the process continuing indefinitely. What is the sum of the areas of all the circles? ### Baby Circle

##### Age 16 to 18Challenge Level

A small circle fits between two touching circles so that all three circles touch each other and have a common tangent? What is the exact radius of the smallest circle? ### Using Geogebra

##### Age 11 to 18 ### A Rational Search

##### Age 16 to 18Challenge Level

Investigate constructible images which contain rational areas. ### Ford Circles

##### Age 16 to 18Challenge Level

Can you find the link between these beautiful circle patterns and Farey Sequences? ##### Age 14 to 16Challenge Level

Investigate the properties of quadrilaterals which can be drawn with a circle just touching each side and another circle just touching each vertex. ### Efficient Packing

##### Age 14 to 16Challenge Level

How efficiently can you pack together disks? ### Tessellation Interactivity

##### Age 7 to 16Challenge Level

An environment that enables you to investigate tessellations of regular polygons ### Two Regular Polygons

##### Age 14 to 16Challenge Level

Two polygons fit together so that the exterior angle at each end of their shared side is 81 degrees. If both shapes now have to be regular could the angle still be 81 degrees? ### Like a Circle in a Spiral

##### Age 7 to 16Challenge Level

A cheap and simple toy with lots of mathematics. Can you interpret the images that are produced? Can you predict the pattern that will be produced using different wheels? ### Spirostars

##### Age 16 to 18Challenge Level

A spiropath is a sequence of connected line segments end to end taking different directions. The same spiropath is iterated. When does it cycle and when does it go on indefinitely? ### LOGO Challenge 12 - Concentric Circles

##### Age 11 to 16Challenge Level

Can you reproduce the design comprising a series of concentric circles? Test your understanding of the realtionship betwwn the circumference and diameter of a circle. ### LOGO Challenge 11 - More on Circles

##### Age 11 to 16Challenge Level

Thinking of circles as polygons with an infinite number of sides - but how does this help us with our understanding of the circumference of circle as pi x d? This challenge investigates. . . . ### Gold Yet Again

##### Age 16 to 18Challenge Level

Nick Lord says "This problem encapsulates for me the best features of the NRICH collection." ### First Forward Into Logo 4: Circles

##### Age 7 to 16Challenge Level

Learn how to draw circles using Logo. Wait a minute! Are they really circles? If not what are they? ### First Forward Into Logo 2: Polygons

##### Age 7 to 16Challenge Level

This is the second in a twelve part introduction to Logo for beginners. In this part you learn to draw polygons. ##### Age 14 to 16Challenge Level

Make five different quadrilaterals on a nine-point pegboard, without using the centre peg. Work out the angles in each quadrilateral you make. Now, what other relationships you can see? ### Lunar Angles

##### Age 16 to 18Challenge Level

What is the sum of the angles of a triangle whose sides are circular arcs on a flat surface? What if the triangle is on the surface of a sphere? ### Circles in Circles

##### Age 16 to 18Challenge Level

This pattern of six circles contains three unit circles. Work out the radii of the other three circles and the relationship between them. ### The Dodecahedron

##### Age 16 to 18Challenge Level

What are the shortest distances between the centres of opposite faces of a regular solid dodecahedron on the surface and through the middle of the dodecahedron? ##### Age 14 to 16Challenge Level

The sides of a triangle are 25, 39 and 40 units of length. Find the diameter of the circumscribed circle. ### Dodecawhat

##### Age 14 to 16Challenge Level

Follow instructions to fold sheets of A4 paper into pentagons and assemble them to form a dodecahedron. Calculate the error in the angle of the not perfectly regular pentagons you make. ### LOGO Challenge - Following On

##### Age 11 to 18Challenge Level

Remember that you want someone following behind you to see where you went. Can yo work out how these patterns were created and recreate them? ### LOGO Challenge 9 - Overlapping Polygons

##### Age 7 to 16Challenge Level

This LOGO challenge starts by looking at 10-sided polygons then generalises the findings to any polygon, putting particular emphasis on external angles ### LOGO Challenge 6 - Triangles and Stars

##### Age 11 to 16Challenge Level

Recreating the designs in this challenge requires you to break a problem down into manageable chunks and use the relationships between triangles and hexagons. An exercise in detail and elegance. ### LOGO Challenge - Circles as Animals

##### Age 11 to 16Challenge Level

See if you can anticipate successive 'generations' of the two animals shown here. ### LOGO Challenge 10 - Circles

##### Age 11 to 16Challenge Level

In LOGO circles can be described in terms of polygons with an infinite (in this case large number) of sides - investigate this definition further. ### LOGO Challenge 1 - Star Square

##### Age 7 to 16Challenge Level

Can you use LOGO to create this star pattern made from squares. Only basic LOGO knowledge needed. ### Arclets Explained

##### Age 11 to 16

This article gives an wonderful insight into students working on the Arclets problem that first appeared in the Sept 2002 edition of the NRICH website. ### Incircles Explained

##### Age 16 to 18 ### Squaring the Circle and Circling the Square

##### Age 14 to 16Challenge Level

If you continue the pattern, can you predict what each of the following areas will be? Try to explain your prediction. ### Semi-square

##### Age 14 to 16Challenge Level

What is the ratio of the area of a square inscribed in a semicircle to the area of the square inscribed in the entire circle? ### Crescents and Triangles

##### Age 14 to 16Challenge Level

Can you find a relationship between the area of the crescents and the area of the triangle? ### Pent

##### Age 14 to 18Challenge Level

The diagram shows a regular pentagon with sides of unit length. Find all the angles in the diagram. Prove that the quadrilateral shown in red is a rhombus. ### Tricircle

##### Age 14 to 16Challenge Level

The centre of the larger circle is at the midpoint of one side of an equilateral triangle and the circle touches the other two sides of the triangle. A smaller circle touches the larger circle and. . . . ### F'arc'tion

##### Age 14 to 16 ShortChallenge Level

At the corner of the cube circular arcs are drawn and the area enclosed shaded. What fraction of the surface area of the cube is shaded? Try working out the answer without recourse to pencil and. . . . ### The Medieval Octagon

##### Age 14 to 16Challenge Level

Medieval stonemasons used a method to construct octagons using ruler and compasses... Is the octagon regular? Proof please. ### Encircling

##### Age 14 to 16Challenge Level

An equilateral triangle is sitting on top of a square. What is the radius of the circle that circumscribes this shape? ### Holly

##### Age 14 to 16Challenge Level

The ten arcs forming the edges of the "holly leaf" are all arcs of circles of radius 1 cm. Find the length of the perimeter of the holly leaf and the area of its surface. ### Three Four Five

##### Age 14 to 16Challenge Level

Two semi-circles (each of radius 1/2) touch each other, and a semi-circle of radius 1 touches both of them. Find the radius of the circle which touches all three semi-circles.