Bill Cosby came to the Capital Centre, that basketball arena by the Beltway, last night and played one-on-twenty-thousand. He won sitting down. Wearing a rainbow-quilted top and red running pants, the comedian delivered his punch lines and then leaned back in his reclining chair, reached over to the nearby coffee table for his cigar, and savored the laughter.

Of course, most people in the audience were too far away to appreciate in the flesh this master of the raised eyebrow and jutted jaw. Instead they were forced to watch the huge closed-circuit TV screens overhead to enjoy his routines. In effect, they were paying a lot of money to watch a cable TV concert film, albeit a very good one.

Cosby is certainly no comedic innovator in the style of Richard Pryor or Lily Tomlin, but he is the best of an old breed that turns universal domestic scenes into slightly exaggerated, hysterical vignettes.

Much of the evening was made up of new material; he spent the first third of the two-hour show discussing the rebellions of his body as he grew older. One of his funniest bits described how your mind will trick you by sending you to the next room to get something and then refusing to tell you what that something is when you get there. With a bewildered look on his face, Cosby created half a dozen squabbling voices inside his mind as they tried to recall the original mission.

In the next segment, Cosby discussed arguments between husbands and wives. He boasted, "I can go for half an hour on just 'That's not what I'm saying,' " and then lit up in a marvelously smug face before moving on to the problems of raising four daughters.

He condensed a year's worth of a mother's harangues at a 13-year-old daughter into one five-minute tirade that brought cascade after cascade of laughter.

Cosby ended the show with an old favorite: his routine on dentists. When he imitated himself trying to talk with half his face deadened by Novocain, the helpless gibberish that resulted had the audience laughing just as helplessly.