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?
Join the midpoints of a quadrilateral to get a new quadrilateral. What is special about it?
Can you find a way to turn a rectangle into a square?
Can you devise a system for making sense of complex multiplication?
Complex numbers can be represented graphically using an Argand diagram. This problem explains more...
Move the point P to see how P' moves. Then use your insights to calculate a missing length.
In how many ways can you fit all three pieces together to make shapes with line symmetry?
Never used GeoGebra before? This article for complete beginners will help you to get started with this free dynamic geometry software.
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.
Investigate what happens to the equation of different lines when you translate them. Try to predict what will happen. Explain your findings.
What happens when we multiply a complex number by a real or an imaginary number?
What happens when we add together two complex numbers?
Two circles of equal radius touch at P. One circle is fixed whilst the other moves, rolling without slipping, all the way round. How many times does the moving coin revolve before returning to P?
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. . . .
Triangle ABC has equilateral triangles drawn on its edges. Points P, Q and R are the centres of the equilateral triangles. What can you prove about the triangle PQR?
Take any triangle, and construct squares on each of its sides. What do you notice about the areas of the new triangles formed?
Cartesian Coordinates are not the only way!
Let's go further and see what happens when we multiply two complex numbers together!
Can you find an efficent way to mix paints in any ratio?
Medieval stonemasons used a method to construct octagons using ruler and compasses... Is the octagon regular? Proof please.
Can you work out how to produce different shades of pink paint?
How did the the rotation robot make these patterns?
Can you decide whether two lines are perpendicular or not? Can you do this without drawing them?
Move the corner of the rectangle. Can you work out what the purple number represents?
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?
Draw some angles inside a rectangle. What do you notice? Can you prove it?
How well can you estimate angles? Playing this game could improve your skills.
Under what circumstances can you rearrange a big square to make three smaller squares?
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.
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?
Position the lines so that they are perpendicular to each other. What can you say about the equations of perpendicular lines?
Use the applet to explore the area of a parallelogram and how it relates to vectors.
An environment that enables you to investigate tessellations of regular polygons
A tool for generating random integers.
Can you explain what is happening and account for the values being displayed?
How does the position of the line affect the equation of the line? What can you say about the equations of parallel lines?
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?
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.
Use the applet to make some squares. What patterns do you notice in the coordinates?
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 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?
Can you work out the fraction of the original triangle that is covered by the inner triangle?
Can you make a right-angled triangle on this peg-board by joining up three points round the edge?
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?
If you continue the pattern, can you predict what each of the following areas will be? Try to explain your prediction.
Where will the point stop after it has turned through 30 000 degrees? I took out my calculator and typed 30 000 ÷ 360. How did this help?
Can you find triangles on a 9-point circle? Can you work out their angles?
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?
Explore the area of families of parallelograms and triangles. Can you find rules to work out the areas?