And I have also activated Emulate 3 button mouse in Preference/ Input.
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Devices like pen tablets and laptop touch pads don't have a scrolling part. But it's still possible to use the functionality of a scroll wheel using the page up and page down buttons on your keyboard. They are the equivalent of scrolling your mouse wheel. Page up (pg up) for scroll up and page down (pg dn) for scroll down. Also if you think that the radius was not what you wanted you can always change that after the operation in the box that appears in the bottom left corner. (Anyone who knows what it's called, please edit this part)