Question

Trans fats: Think about how the prefix trans- is used in naming alkenes.

Answer 1

In an alkene, cis and trans isomers are possible because the double band is rigid, cannot rotate, has groups attached to the carbons of the double bond that are fixed relative to each other, and only occurs with double bonds-possibility that molecule will have different geometries; two different molecules with slightly different properties. 
-Trans-2 ends of chain across the double bond.
While naming Cis-Trans isomers the prefix cis or trans are placed in front of the alkene name when there are cis-trans isomers. 

Answer 2

Alkenes have done bonds and they have two geometrical isomer: cis and trans alkene.  

In cis alkenes identical atoms or groups are positioned on same side of the double bond and in trans alkenes identical atoms or groups are positioned on opposite side of the double bond.  

Unsaturated fatty acids have both cis and trans fats. Elaidic acid is an example of trans found in hydrogenated vegetable oil.