- #1
hypermonkey2
- 102
- 0
Hi,
I found this problem in Do Carmos "differential geometry of curves and surfaces".
it asks to show that the length of a parallel curve B to A given by:
B=A-rn
where r is a positive constant, and n is the normal vector, and A is a closed convex plane curve, positively oriented.
is given by
len(B)=len(A)+2*pi*r
The obvious start would be to integrate both sides under a standard parametrization or the curves, but why is it true that integrating rn will give 2*pi*n exactly?
any insight is appreciated.
Thanks!
I found this problem in Do Carmos "differential geometry of curves and surfaces".
it asks to show that the length of a parallel curve B to A given by:
B=A-rn
where r is a positive constant, and n is the normal vector, and A is a closed convex plane curve, positively oriented.
is given by
len(B)=len(A)+2*pi*r
The obvious start would be to integrate both sides under a standard parametrization or the curves, but why is it true that integrating rn will give 2*pi*n exactly?
any insight is appreciated.
Thanks!