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Which of the following improper integrals is (are) convergent?

1. $\int_{0}^{1} \frac{\sin x}{1-\cos x} d x$
2. $\int_{0}^{\infty} \frac{\operatorname{cox} x}{1+x} d x$
3. $\int_{0}^{x} \frac{x}{1+x^{2}} d x$
4. $\int_{0}^{1} \frac{1-\cos x}{x^{5 / 2}} d x$