Watt's linkage is used to generate approximate straight line motion in automobile suspensions.
Aee how it works.
(Yes I'm using an alpha copy of GX version 3.2)
Look at a point on a sinusoidal curve (y=sin(x)) with a tangent line.
Then, look at a point on the negative of your sinusoidal curve (y=-sin(x)) that is a mirror image of your first point.
Then, notice that these mirror image points have mirror image tangent lines.
