caption: Start with a horizontal number line.
exif: {"Image DocumentName": "Start with a horizontal number line.", "Image ImageDescription": "Extend a vertical number line up from the origin. Plunk in a unit square with its lower left corner at the origin. The sides of the unit square are , and so is the area, since . Since the area is , the sides must have length = since .", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}