表达式2: "f" left parenthesis, "t" , right parenthesis equals 1 half sine left parenthesis, 2 "t" , right parenthesis minus "t" cosine left parenthesis, 2 "t" , right parenthesis minus "u" left parenthesis, "t" minus StartFraction, pi Over 4 , EndFraction , right parenthesis left parenthesis, "t" minus StartFraction, pi Over 4 , EndFraction , right parenthesis sine left parenthesis, 2 "t" minus StartFraction, pi Over 2 , EndFraction , right parenthesisft=12sin2t−tcos2t−ut−π4t−π4sin2t−π2
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表达式3: "y" equals "f" prime left parenthesis, "t" , right parenthesisy=f′t
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表达式4: "y" equals "f" prime prime left parenthesis, "t" , right parenthesisy=f′′t
