
Remember , hence
and the co-ordinate of
is
.
, hence
and the co-ordinate of
is
And from the definition of we know
is the point
Consider the areas of triangle , sector
, and triangle
.
We know from inspection of the above diagram that
Area Area
Area
Which means,
We can ignore all of the halves.
Remember
Divide everything by (as we are in the first quadrant we know
, so we don’t need to worry about the inequality)
Invert everything and change the direction of the inequalities)
I am going to rewrite it as follows
because I like to use less thans rather than greater thans.
Now what happens as tends to
?
Hence by the squeeze theorem
Now we know this limit, we are going to use it to find
Multiply by
If we evaluate the limits,
Hence,
In the next post we are going to use these limits to differentiate sine and cosine functions.