Properties of Shapes

Geometry at KS3 covers angles in shapes and on parallel lines, properties of polygons, congruence, similarity and the constructions needed to draw precise geometric figures.

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Angle Rules

Rule	Statement
Angles on a straight line	Sum = 180°
Angles around a point	Sum = 360°
Vertically opposite angles	Are equal
Angles in a triangle	Sum = 180°
Angles in a quadrilateral	Sum = 360°

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Angles on Parallel Lines

When a transversal crosses two parallel lines:

Angle pair	Shape formed	Relationship
Corresponding angles	F-shape	Equal
Alternate angles	Z-shape	Equal
Co-interior (same-side interior) angles	C-shape	Sum = 180°

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Triangle Types and Properties

Type	Properties
Equilateral	All sides equal; all angles 60°
Isosceles	Two sides equal; two base angles equal
Scalene	No sides or angles equal
Right-angled	One angle = 90°
Obtuse	One angle > 90°