4. Find the approximate diameter of the
moon if an observer on the earth measures an angle of 0.5^{0}
from the top to the bottom of the disk when the moon is 240.000
km away.
Solution:
Let O be the eye of the observer. C is the centre
of the moon, r be the distance from O to C, and DE be a diameter
of the moon perpendicular to OC. Finally, Let A and B be the points
where the circle of radius r centered at O intersects the moon.
Then r is the approximate distance at O intersects the moon. Then
r is the approx. distance from the earth to the moon, and DE is
approx. S, where S = l (ACB).
Since r = 240,000 is probably accurate to only
two significant figures. Thus the most we can say is that the diameter
» 2100 km
5. Find the interior angles of a regular polygon of 10 sides
in radians.
Solution

Index
1.1 Angles (Radians & Degrees)
1.2 Arc Length & Area of the circle
Supplementary Problems
Chapter 2
