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Review what you know about the angles and arcs of circles below. 

  1. A circle is divided into nine congruent sectors. What is the measure of each central angle?

    Recall that a whole circle is .

  2. In the diagram at right, what are and if ?

    Refer to the Math Notes in this lesson.

    Notice the relationship between and .

    Circle with points, in order, a, b, c, d, e, solid line segments from, c, to, d, and from, c, to a, dashed line segments from, b, to d, and from, b, to a.

  3. In at right, and units. What are and the length of ? What is the area of the smaller sector?

    What portion of the circumference is ?

    Use the same method as above to find the area of the smallest sector.

    Circle with center, c, points, a, and, b, with line segments from, c, to a, and from c, to b.