Sine integral
From specialfunctionswiki
The sine integral is defined by $$\mathrm{Si}(z) = \displaystyle\int_0^z \dfrac{\sin t}{t} dt; |\mathrm{arg} z|<\pi.$$
The sine integral is defined by $$\mathrm{Si}(z) = \displaystyle\int_0^z \dfrac{\sin t}{t} dt; |\mathrm{arg} z|<\pi.$$
