In this situation, if the spouse is the sole beneficiary of the qualified trust and is more than 10 years younger than the IRA owner, the IRA owner may use the Joint Life Expectancy Table to calculate her RMD. If the trust is not a qualified trust, however, the IRA owner must use her own age and the Uniform Lifetime Table to calculate her RMD. 

If the spouse is not 10 years younger than the IRA owner, the RMD was be calculated the standard way- Dividing the previous year's December 31 IRA balance by the divisor found in the Uniform Lifetime Table.