Digital Library of Mathematical Functions
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6 Exponential, Logarithmic, Sine, and Cosine IntegralsProperties6.3 Graphics

Figure 6.3.3 (See in context.)

See accompanying text
Figure 6.3.3: |\mathop{E_{1}\/}\nolimits\!\left(x+iy\right)|, -4\leq x\leq 4, -4\leq y\leq 4. Principal value. There is a cut along the negative real axis. Also, |\mathop{E_{1}\/}\nolimits\!\left(z\right)|\to\infty logarithmically as z\to 0.