It is possible to show that d d θ tan ⁡ θ = sec 2 ⁡ θ {\displaystyle {\frac {d}{d\theta }}\tan \theta =\sec ^{2}\theta } by squeezing, as follows.
Có thể chỉ ra rằng d d θ tan ⁡ θ = sec 2 ⁡ θ {\displaystyle {\frac {d}{d\theta }}\tan \theta =\sec ^{2}\theta } bằng định lý kẹp như sau.