# 2d and 3d shape notes

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- Created by: louisepardoe
- Created on: 28-03-16 10:48

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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 in a quadrilateral add up to 360 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…

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