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$\lim _{t \rightarrow 0^{+}} \frac{1}{t^3} \int_0^{\frac{\pi}{4}} \mathrm{~d} \theta \int_0^{\frac{t}{\cos \theta}} \frac{\sin \left(r^2 \sin \theta \cos \theta\right)}{\sin \theta} \mathrm{d} r=$
                        
不再提醒