Put simply, you cannot calculate it by hand. A calculator does it through a very complicated iterative process. You can estimate with a series (Taylor or Maclaurin), but those are approximations.
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But you can totally calculate cos(45) by hand.
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No, you can't. You can memorize the values, though.
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Cause cos(45) is sqrt(2)/2, right?
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Edited by HurtfulTurkey: 10/16/2013 7:32:30 PMcos(45) := sqrt(2)/2 The := means 'equality by definition'. You're not actually calculating it, you're just stating that that's what it equals without showing any work. It equals sqrt(2)/2 the same way 1+1 = 4-2.