Select the Line button and the prompt reads:
Give Start Point:
Select the quadrant point snap at the bottom of the outer circle (Point 1 in the diagram). A dynamic line will be drawn from this point to the cursor. The prompt now reads:
Give Next Point:
Draft it has remembered that the X, Y input option was set when drawing the last circle so either 1) hit the key or click the Snap button . Now select the quadrant point snap at the top of the outer circle (Point 2 in the diagram).
or 2) just position the cursor on the circumference of the largest circle near to Point 2 and hit and click to accept the quadrant point selected. This is a Keyboard Snap and eliminates the need to hit F7.
We will now use this line to start the side view.
If you wish you can 'right-click' the mouse to finish drawing lines. Alternatively selecting the next command would do the same.
Select the Offset button and the prompt reads:
Give Line/Arc/Circle to Offset:
Select the 'Line 1' shown in the diagram and the prompt now reads:
Give Point to Offset To:
As you move the cursor a dynamic offset moves parallel to the 'Line 1'. The Input Option has been set to Distance and you will see a dynamic dimension between 'Line 1' and the dynamic offset. Either 1) Type '100' and hit Click to place the new offset line when the dynamic dimension reads 100.00.