1. Objectives
1. Find arc length of a circle
2. Find area of a sector
3. Solve apparent size problems

2. A
sector of a circle is the region
bounded by a central angle and the
intercepted arc.
 The arc length is some fraction of
the circumference.
 The sector area is the same fraction
of the circle’s area.

3. θ
= 60 and r = 12
 Arc length = s =
circumference
or
 Sector
Area = K =
of the

4.  For
 In
θ in degrees:
radians:

5. A
sector of a circle has arc length 6
cm and area 75cm2. Find its radius
and central angle measure.

6. A
sector has perimeter 16 cm and
area 15 cm2. Find its radius r and arc
length s.

7. = 6 and θ = 2π/3
 Find the arc length and sector area.
r

8.  How
big a far away object looks
depends on its size and also the
angle that it subtends at our eyes.
 This angle is the object’s apparent
size.

9.  Jupiter
has an apparent size of 0.01
when it is 8x108 km from Earth. Find
the approximate diameter of Jupiter.

10.  At
its closest approach, Mars is about
5.6 x 107 km from Earth and its
apparent size is about 0.00012
radians. What is the approximate
diameter of Mars?