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Joey used congruent triangles to create a regular decagon.

  1. What kind of triangles is he using?

    If the triangles are congruent, what does that mean for the ''radius'' lengths?
    The radius goes from the center of the figure to a vertex on the figure.

  2. Find the three angle measures of one of the triangles. Explain how you know.

    If there are triangles, what is the measure of each central angle?

    If this is an isosceles triangle, what is the measure of the other two base angles?

  3. If the area of each triangle is square inches, then what is the area of the regular decagon? Show all work.

    The total area is equal to the area of all of these triangles.