Angles - points, lines and parallel lines

There are 80 NRICH Mathematical resources connected to Angles - points, lines and parallel lines
Isosceles Seven
problem

Isosceles Seven

Age
14 to 16
Challenge level
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Is it possible to find the angles in this rather special isosceles triangle?
Triangle in a Trapezium
problem

Triangle in a Trapezium

Age
11 to 16
Challenge level
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Can you find and prove the relationship between the area of a trapezium and the area of a triangle constructed within it?
Using GeoGebra
article

Using GeoGebra

Never used GeoGebra before? This article for complete beginners will help you to get started with this free dynamic geometry software.
Polygon Rings
problem

Polygon Rings

Age
11 to 14
Challenge level
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Join pentagons together edge to edge. Will they form a ring?