, (S1是Rt△A1A2O的面积); , (S2是Rt△A2A3O的面积); , (S3是Rt△A3A4O的面积);…
问题:
=3, =0.5, =6, = , =0.
根据以上算式,回答:
①若x<2,则 =;
② =.