by Julieanne Kost
When using the Crop tool, moving your cursor outside of the Crop changes the icon to a double headed arrow, clicking and dragging (outside of the crop) will rotate the image (straightening a horizon for example).
Command (Mac) / Control (Win) toggles to the Angle tool while cropping. Using a straight line in the image, for reference click and drag over the reference line (such as a horizon) to straighten.
Cmd+ Opt /Ctrl + Alt + drag with the Crop tool swaps to Angle tool and displays an angled Grid Overlay