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## Main Question or Discussion Point

I want to design a crank mechanism. I found this page on Wikipedia

https://en.wikipedia.org/wiki/Piston_motion_equations

Relating from this diagram, is x the max stroke of the piston ?, or is it PO-(max stroke of piston) ?

And why is l^2 = r^2 + x^2 - 2*r*x*cos(A)

Shouldn't it be, l^2 = r^2 + OP^2 - 2*r*OP*cos(A) ?

https://en.wikipedia.org/wiki/Piston_motion_equations

Relating from this diagram, is x the max stroke of the piston ?, or is it PO-(max stroke of piston) ?

And why is l^2 = r^2 + x^2 - 2*r*x*cos(A)

Shouldn't it be, l^2 = r^2 + OP^2 - 2*r*OP*cos(A) ?