Get out your old Jeppesen CR round flight computer. No matter what temperature you put in, if you are at FL 350 and doing mach .80, your indicated airspeed will be 272 knots. The charts in your manual will show the same thing. The relationship between mach and IAS is not changed by temperature. I cannot really explain why, but perhaps someone smarter than me can. The airspeed indicator in your airplane that has mach in the side also is just a mechanical relationship between mach number, altitude, and indicated airspeed. Temperature does not factor into it. The temperature will make your mach number different, but I am saying if you fly a constant mach, your indicated airspeed will not change.