160 likes | 406 Views
Area of Regular Polygons. Brett Solberg AHS ‘11-’12. Warm-up. 1) What is the measure of an interior angle in a regular hexagon? hint (n-2)*180 2) Find the value of x and y in the regular triangle. Which HW problems should we review?. Today’s Agenda. Mini-Quiz Area of Regular Polygons
E N D
Area of Regular Polygons Brett Solberg AHS ‘11-’12
Warm-up • 1) What is the measure of an interior angle in a regular hexagon? hint (n-2)*180 • 2) Find the value of xand y in the regular triangle. • Which HW problems should we review?
Today’s Agenda • Mini-Quiz • Area of Regular Polygons • finding interior angles • finding angles created by radii • using apothem • applying properties of special right triangles • Announcements • 4th Quarter Change – Only one retake for the quarter
Regular Polygon • What is a polygon? • an enclosed figure with at least 3 straight sides. • What is a regular polygon? • a polygon where all the sides and angles are congruent
Radius and Apothem • Any regular polygon can be circumscribed. • Radius: distance from the center to the vertex. • Apothem: perpendicular distance from the center to a side. • Draw and label the other radii and apothems.
Area of a Regular Polygon • The area of a regular polygon is half the product of the apothem and the perimeter. • How do we find perimeter? • p = ns • n= number of sides • s = length of one side
Example 1 • Find the area of a regular decagon with a 12.3 inch apothem and a side length of 8. • Decagon = • Perimeter = • Area =
Example 2 • Find the area of a regular polygon with twenty 12 inch sides and a 37.9 inch apothem. • Perimeter = • Area =
Area of a Polygon • What if we aren’t given the apothem? • fill in missing angles • use properties of special right triangles 30 60
Equilateral Triangle • Label the radii and apothems. • What angles do they create?
Square • Label the radii and apothems. • What angles do they create?
Example 1 – Regular Pentagon • Label the radii and apothem • Find the angles in the regular pentagon.
Regular Hexagon • Label the radii and apothem • Find the angles in the regular pentagon.
Example 3 • Find the area of a regular triangle with a side of 8 inches. in
Example 4 • Find the area of a square with the radius of 8 cm. 8 cm
Homework • 10-3 Worksheet