4.20若已知 (t)arrow F(jomega ) ,试求下列函数的频谱。-|||-(1)tf(2t)-|||-(2) (t-2)f(t)-|||-(3) dfrac (df(t))(dt)-|||-(4) f(1-t)-|||-(5) (1-t)f(1-t)-|||-(6) f(2t-5)-|||-(7)(int )_(-infty )^1-dfrac (1{2)t}f(t)dt-|||-(8) ^itf(3-2t)-|||-(9) dfrac (df(t))(dt)neq dfrac (1)(pi t)