Infinity on High with a 54% decline during a post-Grammy week. The album rose to number three in its third week with 79,000 units sold. In its fourth week, the disc slipped to number four and sold 67,000 copies. "Infinity on High"s sales again fell in its fifth week, moving 58,000 copies and descending to number eight on the chart. In its sixth and last week in the top ten it fell to number nine and sold 43,000 copies. In April 2007, the album was certified Platinum by the Recording Industry Association of America (RIAA), denoting the shipment of one million copies. It
Plane at infinity does make it look "special" in comparison to the other planes of the space. If the affine 3-space is real, formula_2, then the addition of a real projective plane formula_3 at infinity produces the real projective 3-space formula_4. Since any two projective planes in a projective 3-space are equivalent, we can choose a homogeneous coordinate system so that any point on the plane at infinity is represented as ("X":"Y":"Z":0). Any point in the affine 3-space will then be represented as ("X":"Y":"Z":1). The points on the plane at infinity seem to have three degrees of freedom, but homogeneous coordinates are equivalent