# Question about Length of Action of Involute gears

1. Nov 5, 2015

### A330NEO

1. The problem statement, all variables and given/known data
Length of action Z(Length of line of action) is $Z=\sqrt{(r_{p}+a_{p})^{2}-(r_{p}cos\phi )^{2}}+\sqrt{(r_{g}+a_{g})^{2}-(r_{g}cos\phi )^{2}}-Ccos\phi$ How can I drive it?

2. Relevant equations

3. The attempt at a solution

2. Nov 6, 2015