+265 ft BIG idea Measurement An arc length is a fractional part of the circumference of a circle. The area of a sector is a fractional part of the area of a circle. Task 2 The stained glass circle-head window has a 2-in. wide frame. The grills divide the semicircular glass pane into four congruent regions. a. What is the area of the blue region? b. What is the outside perimeter of the window frame? 6 in. 28 in. BIG idea Similarity