2d and 3d shape notes

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Geometry

• angles in a triangle add up to 180 degrees
• angles on a straight line add up to 180 degrees
• angles round a point add up to 360 degrees
• exterior angle of a triangle=sum of opposite interior angles
• isoseles triangles have 2 sides the same and 2 angles the same

Parallel lines

angles around parallel lines

• when a line crosses two parallel lines, it forms special sets of angles
• the two bunches of angles formed at the points of intersection are the same
• there are actually only two different angles involved and they add up to 180 degrees
• vertically opposite angles are equal

alternate,allied and corresponding angles

• alternate angles are the same and are found in a z shape
• allied angles add up to 180 degrees and are found in a c or u shape
• corresponding angles are the same and are found in an f shape

Polygons

regular polygons

• regular polygons have equal sides and equal angles
• equilateral triangle-3 sides
• square-4 sides
• pentagon-5 sides
• hexagon-6 sides
• heptagon-7 sides
• octagon-8 sides
• nonagon-9 sides
• decagon-10 sides

Interior and exterior angles

• sum of exterior angles is 360 degrees
• sum of interior angles=(n-2)x180
• in regular polygons, you can find the exterior angle by dividing 360 by the number of sides
• in regular…