There are a few things you need to know before starting to draw a curved line in Illustrator. First, make sure that your cursor is on the line you want to create. Second, make sure that the line is long enough so that it covers the entire canvas, and third, make sure that the line is straight. Finally, use the arrow keys to move the line around and make it more or less curved.
Design with the Curvature Pen Tool Illustrator Tutorial
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