Справка LibreOffice 7.4
Returns the tangent of a complex number. The tangent of a complex number can be expressed by:
МНИМ.TAN(КомплексноеЧисло)
Complex_number is a complex number whose tangent is to be calculated.
=МНИМ.TAN("4-3i")
возвращает 0,00490825806749606-1,00070953606723i.
=IMTAN(2)
returns -2.18503986326152 as a string. The imaginary part is equal to zero, so it is not displayed in the result.