Я кое-что поменял, код стал немного компактнее... Может так будет легче разобраться:
ex_part\speed = Rnd(0.1,0.11)
a1# = (Sin(90 - Abs(roll))^2) / (Cos(90 - Abs(roll))^2)
b1# = (Tan(90 - Abs(roll))^2) / (Tan(90 - Abs(pitch))^2)
a2# = (Cos(90 - Abs(pitch))^2) / (Sin(90 - Abs(pitch))^2)
b2# = (Cos(90 - Abs(roll))^2) / (Sin(90 - Abs(roll))^2)
a3# = (Sin(90 - Abs(pitch))^2) / (Cos(90 - Abs(pitch))^2)
b3# = (Tan(90 - Abs(pitch))^2) / (Tan(90 - Abs(roll))^2)
ex_part\xspeed = Sqr(ex_part\speed^2 / (1 + a1 + b1))
ex_part\yspeed = Sqr(ex_part\speed^2 / (1 + a2 + b2))
ex_part\zspeed = Sqr(ex_part\speed^2 / (1 + a3 + b3))