130 likes | 294 Views
Area and Perimeter: Areas of Regular Polygons. inscribed polygon circumscribed circle. Review: Inscribed Polygons & Circumscribed Circles. Inscribed means written inside. Circumscribed means written around (the outside).
E N D
inscribed polygon circumscribed circle Review: Inscribed Polygons & Circumscribed Circles Inscribed means writteninside Circumscribed means writtenaround (the outside) Def: A polygon is inscribed in a circle & the circle is circumscribed about the polygon when each vertex of the polygon lies on the circle. Def:A ________________is a polygon that is equiangular & equilateral.
Inscribed Regular Polygons & Triangles Inscribed Regular Pentagon Total of Interior Angles = ___________ Each Interior Angle = ______________ 5 congruent isosceles triangles Total of Central Angles = _________ Each central angle = _____________
Parts of a Regular Polygon • A stands for Area • A(nonagon) is the area of a regular 9-sided figure. • n is the number of sides of a regular polygon • p is perimeter, r is radius, s is side • a is apothem • ____________ – The line segment from the center of a regular polygon to the midpoint of a side or the length of this segment. • Sometimes known as the ______________, or the radius of a regular polygon’s inscribed circle.
O a s Y X Regular Polygon Area Theorem Given: an inscribed regular n-gon (shown as an octagon) A(n-gon) = Regular Polygon Area Theorem: The area of a regular polygon is ___________________________________________ ____________________________________________________
O (Regular Octagon) M Y X Regular Polygon Terminology _______________________- the center of the circumscribed circle (O). _______________________- the distance from the center to a vertex (OX). _____________________________- an angle formed by 2 radii drawn to consecutive vertices. ( ) ____________________________- the (perpendicular) distance from the center of the polygon to a side. (OM)
r = . Find a, p, A. r a 45 x s Example: Square
a = 4. Find r, p, A . r a 30 x s Example: Equilateral Triangle
a = . Find r, p, A. r a 60 x s Example: Regular Hexagon
r = 10; Find a, p, A. a r x X s 70 Regular Nonagon
Examples r r a a
More Examples s r r r a a a x x x 1.r = , find A. 2.a = 6, find A. 3.a = 8, find p. 4.r = 12, find s. 5.s = 8, find r.