It seems to be common to hear x = 3 sin(α)
pronounced as
x equals to three sine alpha
I would read x = 3 sin(α)
as "x equals three ...", and I believe this to be the correct pronunciation and hear it more commonly among mathematicians in formal settings and among well-read English-first-language speakers.
So what's origin of the "equals to" (mis?) pronunciation? How did it come to be so pervasive?