Angles in Parallel Lines and Polygons

• How to construct a perpendicular bisector of a line segement-

  Step 1: Draw a straight line of any length

  Step 2: Open up your compass so that it is more than half of the line you draw

  Step 3: Put the pointy bit of the compass on one end of the line and draw an arc

  Step 4: Repeat with other end of line- don't change compass lengths!!

  Step 5: Draw a line through the middle of the arc where it intersects
• Alternate angles are equal. They make the shape Z
• Corresponding angles are equal. They make the letter F
• Co-interior angles sum to 180 degrees
• Alternate, corresponding and co-interior angles

  
• Only parallel lines are co-interior angles- do not assume!!!
• Angles around a point sum to 360 degrees
• Angles on a straight line sum to 180 degrees
• The sum of angles in any polygon is

  (Number of sides- 2)×180°
• Interior and exterior angle sum to 180°
• Sum of the exterior angles in a polygon is always 180°
• The size of each exterior angle is

  360÷number of sides
• The size of each interior angle is

  Sum of interior angles÷number of sides