1. Evolute and Involute
Let 𝐶 and 𝐶1 are two one-one correspondence space curves
such that tangent at any point on 𝐶 is a normal to the
corresponding point on 𝐶1 then
C is called evolute of 𝐶1 and
𝐶1 is called involute of 𝐶.
i.e. if C is evolute of 𝐶1 then
a. 𝐶1 lies in the tangent surface of C
b. tangent vectors to 𝐶 and 𝐶1 are perpendicular

2. Red curve Blue curve
- Evolute
- Involute

3. Red curve Blue curve
- Evolute
- Involute

4. Dotted curve Circle
- Evolute
- Involute