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### Number and algebra

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# Perpendicular Lines

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### Intersections

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Age 14 to 16

Challenge Level

- Problem
- Getting Started
- Student Solutions
- Teachers' Resources

You may want to take a look at Parallel Lines before attempting this problem.

Take a look at the interactivity below which allows you to move the vertices and make different squares.

The adjacent sides of a square are perpendicular to each other.

How would you describe going from one vertex to the next? And to the next? And to the next?...

Change one equation in this pair of simultaneous equations very slightly and there is a big change in the solution. Why?