Position of an oscillating piston

[Runaway]

Homework Statement

Consider the simplified single-piston engine
in the figure. The piston rod oscillates in
simple harmonic motion. The wheel of radius
1.89 m rotates at a constant angular speed of
6.7 rad/s.

(my own paint version of the figure)
If the piston is fully extended at time t = 0,
find the position of the piston at 6.14 s. Let
the origin (x = 0) be the center of the wheel.
Answer in units of m.

Homework Equations

Xt= A cos(wt)

The Attempt at a Solution

If I understand the diagram correctly, it's trying to show a wheel with a peg (the black dot) stuck through an slider that let's the piston move horizontally with the peg but not vertically. so I tried just plugging it in and got:
1.89*cos(6.7*6.14)= -1.80709

 

[collinsmark]

If I understand the diagram correctly, it's trying to show a wheel with a peg (the black dot) stuck through an slider that let's the piston move horizontally with the peg but not vertically. so I tried just plugging it in and got:
1.89*cos(6.7*6.14)= -1.80709

The x-component of the peg's position varies between +1.89 m and -1.89 m.

If you want to find the position of the piston, you need to add on the length of the rod (between the piston and the peg). But I can't tell for sure what the length of the rod is, based on the diagram (perhaps in your version of the diagram it's more clear). My point is that you have to add the length of the rod to the peg's position to determine the position of the piston.