generic_spct and derived
classes. \
The functions are applied to the spectral data, not the wavelengths. The
quantity in the spectrum to which the function is appled depends on the class
of x and the current value of output options.
"cos"(x)
"sin"(x)
"tan"(x)
"acos"(x)
"asin"(x)
"atan"(x)
cospi.generic_spct(x)
sinpi.generic_spct(x)
tanpi.generic_spct(x)