IMCOS function
Returns the cosine of a complex number. The cosine of a complex number can be expressed by:
cos(a+bi) = cos(a)cosh(b) - sin(a)sinh(b)i
IMCOS(Complex_number)
Complex_number is a complex number whose cosine is to be calculated.
=IMCOS("4-3i")
returns -6.58066304055116-7.58155274274654i.
=IMCOS(2)
returns -0.416146836547142 as a string.
The imaginary part is equal to zero, so it is not displayed in the result.