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Properties of Two Dimensional Figures. Unit 7. Polygons. Unit 7: Properties of Two Dimensional Figures. Polygons and Their Formulas. Polygon. _______________ - A two dimensional figure with these characteristics: It is made of straight line segments.
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Polygons Unit 7: Properties of Two Dimensional Figures
Polygons and Their Formulas Polygon • _______________ - A two dimensional figure with these characteristics: • It is made of straight line segments. • Each segment touches exactly two other segments at their endpoints. • It is closed. This means that it divides the plane into two distinct regions, one inside and the other outside the polygon.
Polygons and Their Formulas Convex Polygon • _______________ - A polygon in which all interior angles measure less than 180˚. • _______________ - A polygon with at least one interior angle that measures more than 180˚. • _______________ - A polygon in which all sides and interior angles are congruent. • In convex polygons, the sum of the interior angles is _______________. Concave Polygon Regular Polygon (n – 2)180
Polygons and Their Formulas • The measure of each interior angle of a regular polygon is . • In convex polygons, the sum of the exterior angles is . • The measure of each exterior angle of a regular polygon is .
Examples • What is the interior angle sum of a hexagon? • What is the measure of an exterior angle of a regular heptagon? • What is the measure of an interior angle of a regular decagon?
Examples • If a regular polygon has an interior angle sum of 1980˚, how many sides does the polygon have? • If the measure of an exterior angle of a regular polygon is 45˚, haw many sides does the polygon have? What is the measure of the interior angle?
Examples • Circle the figures that are polygons. If the figure is not a polygon, give a justification.
Examples • Determine if the polygons below are convex or concave. Circle the convex polygons.
Examples • Match the name of the polygon with its representative figure. E F A C B G D
Examples • Is there more than one way to name a polygon? Explain the procedure for naming polygons. Give an example and a non-example
Examples • Give a congruence statement that would have to be true if the figure above was a regular hexagon.
Circles and Angles Unit 7: Properties of Two Dimensional Figures
Theorems • If a line is perpendicular to a radius of a circle at a point on the circle, then the line is tangent to the circle.
Theorems • If two segments are tangent to a circle from the same external point, then the segments are congruent.
Theorems • If a radius (or diameter) is perpendicular to a chord, then it bisects the chord.
Theorems • If a quadrilateral is inscribed in a circle, then its opposite angles are supplementary.
Postulates • The measure of a minor arc is equal to the measure of its central angle. • The measure of a major arc is equal to 360˚ minus the measure of its central angle.