/inf ci(x) = | cos(t)/t dt /x

for x > 0. Its definition is similar to the complementary sine integral, and not to the sine integral itself, since ci(0) = infinity.

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The cosine integral is a function defined by:

/inf ci(x) = | cos(t)/t dt /x

for x > 0. Its definition is similar to the complementary sine integral, and not to the sine integral itself, since ci(0) = infinity.