Tan(11.5)=0.2034523 approximately. It cannot be represented exactly because the decimal goes on forever and it can't be expressed as a fraction.
Tan(11.25) (eleven and a quarter degrees) can be found exactly in terms of irrational numbers because it's 45/4 and tan(45)=1 exactly, and there are formulas for finding the tangents of half angles, but there is still no exact decimal or fraction.