The transmission angle for the fourbar mechanism shown above is
defined as the acute angle between the velocity difference vector ** V32 **
between links three and four and the absolute velocity vector **Vout** of
the output link (link four).

Due to the fact that **V32** will always be perpendicular to link
three and **Vout** will always be perpendicular to link four at the three-four connection point, the transmission angle gamma can be found
using the following formula:

gamma = theta4-theta3