A dot starts at the point (1,0) and turns anticlockwise. Can you estimate the height of the dot after it has turned through 45 degrees? Can you calculate its height?
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?
A circle rolls around the outside edge of a square so that its circumference always touches the edge of the square. Can you describe the locus of the centre of the circle?
Medieval stonemasons used a method to construct octagons using ruler and compasses... Is the octagon regular? Proof please.
Draw some angles inside a rectangle. What do you notice? Can you prove it?
An environment that enables you to investigate tessellations of regular polygons
If you continue the pattern, can you predict what each of the following areas will be? Try to explain your prediction.
Never used GeoGebra before? This article for complete beginners will help you to get started with this free dynamic geometry software.
Can you make sense of these three proofs of Pythagoras' Theorem?
A right-angled isosceles triangle is rotated about the centre point of a square. What can you say about the area of the part of the square covered by the triangle as it rotates?
The opposite vertices of a square have coordinates (a,b) and (c,d). What are the coordinates of the other vertices?
Is there a relationship between the coordinates of the endpoints of a line and the number of grid squares it crosses?
Construct two equilateral triangles on a straight line. There are two lengths that look the same - can you prove it?
The sine of an angle is equal to the cosine of its complement. Can you explain why and does this rule extend beyond angles of 90 degrees?
Semi-regular tessellations combine two or more different regular polygons to fill the plane. Can you find all the semi-regular tessellations?
Can you work out the fraction of the original triangle that is covered by the inner triangle?
Kyle and his teacher disagree about his test score - who is right?
Explore the area of families of parallelograms and triangles. Can you find rules to work out the areas?
L triominoes can fit together to make larger versions of themselves. Is every size possible to make in this way?
The farmers want to redraw their field boundary but keep the area the same. Can you advise them?
Experiment with the interactivity of "rolling" regular polygons, and explore how the different positions of the dot affects its vertical and horizontal movement at each stage.
The length AM can be calculated using trigonometry in two different ways. Create this pair of equivalent calculations for different peg boards, notice a general result, and account for it.
Using a ruler, pencil and compasses only, it is possible to construct a square inside any triangle so that all four vertices touch the sides of the triangle.
A tool for generating random integers.
How can visual patterns be used to prove sums of series?
Draw some quadrilaterals on a 9-point circle and work out the angles. Is there a theorem?
Can you explain what is happening and account for the values being displayed?
A tilted square is a square with no horizontal sides. Can you devise a general instruction for the construction of a square when you are given just one of its sides?
Can you find triangles on a 9-point circle? Can you work out their angles?
Experiment with the interactivity of "rolling" regular polygons, and explore how the different positions of the red dot affects the distance it travels at each stage.
Show how this pentagonal tile can be used to tile the plane and describe the transformations which map this pentagon to its images in the tiling.
What is the relationship between the angle at the centre and the angles at the circumference, for angles which stand on the same arc? Can you prove it?
Can you make a right-angled triangle on this peg-board by joining up three points round the edge?
Move the point P to see how P' moves. Then use your insights to calculate a missing length.
Draw some isosceles triangles with an area of $9$cm$^2$ and a vertex at (20,20). If all the vertices must have whole number coordinates, how many is it possible to draw?
Join pentagons together edge to edge. Will they form a ring?
How well can you estimate angles? Playing this game could improve your skills.
Investigate what happens to the equation of different lines when you translate them. Try to predict what will happen. Explain your findings.
Can you decide whether two lines are perpendicular or not? Can you do this without drawing them?
Investigate what happens to the equations of different lines when you reflect them in one of the axes. Try to predict what will happen. Explain your findings.
It would be nice to have a strategy for disentangling any tangled ropes...
The points P, Q, R and S are the midpoints of the edges of a non-convex quadrilateral.What do you notice about the quadrilateral PQRS and its area?
Move the corner of the rectangle. Can you work out what the purple number represents?
P is a point on the circumference of a circle radius r which rolls, without slipping, inside a circle of radius 2r. What is the locus of P?
Triangular numbers can be represented by a triangular array of squares. What do you notice about the sum of identical triangle numbers?
We can show that (x + 1)² = x² + 2x + 1 by considering the area of an (x + 1) by (x + 1) square. Show in a similar way that (x + 2)² = x² + 4x + 4
A red square and a blue square overlap so that the corner of the red square rests on the centre of the blue square. Show that, whatever the orientation of the red square, it covers a quarter of the. . . .
Use the applet to explore the area of a parallelogram and how it relates to vectors.
Draw a square. A second square of the same size slides around the first always maintaining contact and keeping the same orientation. How far does the dot travel?
Cartesian Coordinates are not the only way!