How to write an equation in assembler?

Question

OpenGL

I'm trying to get into the assembler, but I can't understand why I get a crooked scene as a result?

scene2 proc x, y, z:DWORD
  ;cos(sin(x-fi)*fi)
  fld x
  fsub fi
  fsin
  fld fi
  fmul
  fcos
  
  mov eax, z
  fstp dword ptr [eax]
  
  ret

scene2 endp