Within an equation, how would I put text directly above other text?

Question

I've seen something a little like this in a textbook I'm reading and I'm not sure how this would be written in LaTeX, can anyone help?

egreg · Accepted Answer

Not sure what it means, but…
documentclass{article}
usepackage{amsmath}

newcommand{sincos}{mathop{begin{array}{@{}l@{}}sincosend{array}Big}}}

begin{document}

[
Z = A sincos k_1x sincos k_1y sincos ckt
]

end{document}

One Answer