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Home > CCG > Chapter 8 > Lesson 8.2.2 > Problem 8-84


Always a romantic, Marris decided to bake his girlfriend a cookie in the shape of a regular dodecagon (-gon) for Valentine’s Day.  

  1. If the edge of the dodecagon is cm, what is the area of the top of the cookie?

    Try splitting the cookie into triangles.
    What information do you already know about these triangles' angles and sides?
    Can you use this to find the area of a single triangle?

    A dodecagon divided into 12 equal parts.

    A dodecagon figure divided into 12 equal parts. One part has a side equal to  6 cm, two angles congruent, two sides congruent and the inside angle at the center 360 divided by 12 degrees.

  2. His girlfriend decides to divide the cookie into congruent pieces. After of the pieces have been eaten, what area of the cookie is left?

    Multiply the area of a single triangle by the number of triangles remaining after some have been eaten.