Step 1) Open up a new document.

Step 2) Create a line of length 2 from the origin and line of length 3 from the origin; something like . Their exact angle doesn’t matter, just something like :

Step 3) Create a 45 degree angle between the 2 line segments:

Step 4) Connect the end points with a tangent arc:

Step 5) Dimension the center of that arc with the point of top line as shown:

Step 6) Create an inscribed circle as shown :

Step 7)  Create a symmetric extrude

Step 8) Finished product. Notice how the symmetric extrude goes up and goes down: