1. Vocabulary for section 2.2 Part II MA418 McAllister Spring 2010

2. A few random terms before we get started Parallel lines (rays, line segments) – lines which lie in the same plane and never intersect. Perpendicular lines – lines which intersect to form 90 degree (or right) angles. Adjacent vertices – vertices that are the endpoints of one side of a polygon.

3. Classifying Polygons – number of sides 3 – triangle 4- quadrilateral 5 – pentagon 6 – hexagon 7 – heptagon 8 – octagon 9 - nonagon 10 – decagon 12 – dodecagon N – N-gon

4. Classifying polygons - by general characteristics Equilateral – all of the sides in the figure are the same length. Equiangular – all of the angles in the figure have the same measure. Regular – all of the sides are the same length and all of the angles have the same measure.

5. Special classifications for specific shapes - TRIANGLES Acute – all three angles are less than 90 degrees Obtuse – one angle is between 90 and 180 degrees Right – one angle is exactly 90 degrees Scalene – all three sides (and angles) are different measures Isosceles – at least (exactly) two sides are the same length. Some triangles may have more than one of these classifications.

6. Special classifications for specific shapes - QUADRILATERALS Trapezoid – has at least (exactly) one pair of parallel sides. Kite – has two pairs of adjacent, congruent sides Parallelogram – has two pairs of parallel sides Rectangle – a parallelogram with at least one right angle Rhombus – a parallelogram with all sides congruent Square – a regular quadrilateral

7. Symmetries – another way to classify figures Reflection symmetry – if there exist a line along which the figure can be folded so that one side matches up exactly with the other side. – This line is called the line of symmetry or the axis of symmetry. Rotation symmetry - if the figure can be turned around a point less than 360 degree and match up. – This point is called the center of rotation.

8. Circles are not Polygons – but they are very special Circle – all the given points equidistant from a given point called the center. Radius – a line segment from the center of a circle to a point on the circle. Diameter – a line segment that goes through the center of the circle and has endpoints on the circle. Circles are symmetrical around the center point and reflective across any diameter.

9. Let’s explore these shapes Get out worksheet #12 – classify each of the shapes on the page with all of the terms in section 2.2 that we’ve discussed. We’ll do one together. Let’s look at the following problems from the book – p. 59, #7, 17