The formula for arc length is l=x°/360•2(pi)r So, we must fill in the variables. l=45°/360•2(pi)4 Then, we slowly simplify step by step. 45°/360= .125 or 1/8 . We then solve the other side 2(pi)4. If we leave it in terms of pi, then it is 8. Now the whole equation, l=.125•8pi. It leads us to the answer 1pi or simply pi. If you want the exact answer round to 3.14.
Answer is pi, or 3.14 depending what the answer must be rounded to.