Find the limit .
Solution：According to the value range and half-angle formula of the cosine function , we have
,
The unit circle is drawn as shown below:
According to the commonly used formula for calculating area , we have
Triangle area sector area,
There is
,
thereby
,
Therefore, when , there is
,
From this, using the clamping criterion of the function , we get
,
so
.
Note : In fact, the results of this example can be obtained directly from the continuity of elementary functions studied later in this chapter .
