Looking at the Perigee Visual Dictionary Of Signing by Butterworth and Flodin, I find the following descriptions for "dance" and "imagine":
dance - point the left flat upturned hand to the right; then swing the downturned fingers of the right V hand from side to side over the left palm.
Memory aid: The fingers of the V hand represent the dancing legs of a person.
imagine - Hold right I hand near forehead with palm facing in. Move the I hand forward and upward in a few rolling circles.
Memory aid: Suggest futuristic thoughts coming from the mind.
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