表达式3: "f" left parenthesis, "t" , right parenthesis equals "I" times cosine left parenthesis, "t" , right parenthesis plus "Q" times sine left parenthesis, "t" , right parenthesisft=I·cost+Q·sint
3
表达式4: "f" Subscript, 1 , Baseline left parenthesis, "t" , right parenthesis equals "I" times cosine left parenthesis, "t" , right parenthesisf1t=I·cost
4
表达式5: "f" Subscript, 2 , Baseline left parenthesis, "t" , right parenthesis equals "Q" times cosine left parenthesis, "t" , right parenthesisf2t=Q·cost