/x is an even function, so only one side needs to be considered.

In the unit circle, it can be 0.

1 & lt； x/sinx & lt； 1/cosx

Go find Cox

Sinks

/x & lt； 1

X on both sides tends to 0 and takes the limit respectively.

The limit on the left is 1 and the limit on the right is 1.

Then sinx is obtained by pinch law.

The limit of /x when x→0 is 1.