what is the true relative error?
Select one:
1. (Present Approximation - Truth) / Previous Approximation
2. (Truth - Approximation) /Truth
3. Truth - Approximation
4. (Approximation - Truth) /Approximation
5. (Previous Approximation - Present Approximation) / Previous Approximation
6. (Present Approximation - Previous Approximation) / Present Approximation
7. Present Approximation - Previous Approximation