| Term | Definition |
|---|
| (n-2)180 | the formula for sum of the interior angles of a polygon |
| polygon | a closed figure formed by joining segments (sides) at their endpoints |
| regular polygon | a polygon with congruent sides |
| diagonal of a polygon | a segment that connects non-consecutive vertices |
| formula for the # of diagonals of a polygon | x(x-3)/2 is the formula for: |
| triangle | a three sided figure whose sum of the interior angles is 180 degrees |
| triangle inequality | the sum of the lengths of any two sides is greater than the third side |
| equilateral triangle | all sides are congruent |
| isosceles triangle | at least two sides are congruent |
| scalene triangle | no sides are congruent |
| acute triangle | all angles in a triangle are between 0 and 90 degrees |
| obstuse triangle | one angle in a triangle is between 90 and180 degrees |
| right triangle | one angle in a triangle is exactly 90 degrees |
| quadrilateral | a polygon with 4 sides |
| parallelogram | a quadrilateral with opposite sides parallel and congruent |
| trapezoid | a quadrilateral with only one pair of parallel sides |
| rectangle | a parallelogram with 4 congruent angles |
| rhombus | a parallelogram with 4 congruent sides |
| square | a rectangle with 4 congruent sides |
| pentagon | a polgyon with 5 sides |
| hexagon | a polygon with 6 sides |
| heptagon (septagon) | a polygon with 7 sides |
| octagon | a polygon with 8 sides |
| nonagon | a polygon with 9 sides |
| decagon | a polygon with 10 sides |
| dodecagon | a polygon with 12 sides |
| n-gon | a polgyon with many sides |
| circle | a plane figure composed of all points measuring the same distance from a point in the center |
| compass | a tool used to draw a circle |
| radius | a segment joining the center of a circle to any point on the circle |
| chord | a segment joining two points on a cirlce |
| diameter | a chord passing through the center of a circle |
| circumference | the perimeter of a circle |
| circumference formula | C = 2(pi)r or C=d(pi) |
| central angle | an angle whose vertex is the center of a circle |
| parallel lines (//) | two or more lines that will never intersect |
| perpendicular lines | lines that intersect to form four 90 degree angles |
Combine with other sets
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