riddle - Why would five hundred and five be same as one?

Grandpa was in his crazy math mood again.

"using rot13 and your math knowledge prove to me that

505 = 1"

He said.

Really? Can you?

HINT

Think Trigonometry

Answer

Here's one possible solution:

1. $505 = 1$ : Given
2. $DV = 1$ : By Romanizing left
3. $V = 1/D$
4. $CV = C/D$ : Multiply through by 100
5. $(PI)= C/D$ : By Rot(13)ing left
6. $Dπ = C$

By the circumference formula for a circle (C= πD),the left and right are equivalent

Q.E.D.