How to keep both handles equal distance while dragging one of them?

If you have an anchor points with handles, how can you drag one handle and cause the other handle to move to maintain symmetry (equal length)? A lot of tutorials say to hold down the shift key with the direct selection tool but that only restrain the angle of the line between the anchor and the handle. I tried the ctrl key, alt key, combination of all three keys but nothing works.

The only solution I found is to use the anchor point tool (upside down V shape) to drag out a new line from the anchor point. This new line will have symmetrical anchors initially. But having to drag out new handles instead of moving it makes it hard to make minor adjustment.

Is there another way?