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'Curved Square' printed from http://nrich.maths.org/
Why do this problem?
draws together coordinate geometry, equations of circles, and surds, and can also be approached using integration.
Show the diagram
(also available as a PowerPoint slide
Give students time to study the diagram, and make notes about what they know and what they can work out. Pose the problem of finding the shaded area, and after some thinking time bring the class together to discuss possible strategies.
Two possible strategies are outlined in the following worksheets:
You could outline the general methods to the class and give them time to solve the problem for themselves, offering the worksheet as a prompt if they get stuck.
Allow time at the end of the lesson for students to compare the different approaches.
What information will we need to find the area?
What symmetries are present in the diagram? Does the area split up in any obvious ways?
Which would be the easiest arcs to work with? Why?
How can integration be used to find the area?
Find the areas of the other parts of the diagram.
Set up a similar problem using parabolas instead of circles.
The worksheets suggest a suitable coordinate grid, and offer prompts for students to follow.