But it is ________ that publishers, to stay in business, need to bring out a large num
A.spontaneous
B.boring
C.elementary
D.evident
A.spontaneous
B.boring
C.elementary
D.evident
证明下列各式. (1)f1(t)*f2(t)=f2(t)*f1(t); (2)f1(t)*[f2(t)*f3(t)]=f3(t)*[f1(t)*f2(t)]; (3)a[f1(t)*f2(t)]=[af1(t)]*f2(t)=f1(t)*[af2(t)](a为常数); (4)eat[f1(t)*f2(t)]=[eatf1(t)]*[eatf2(t)](a为常数); (5)[f1(t)+f2(t)]*[g1(t)+g2(t)]=f1(t)*g1(f)+f2(t)*g1(t)+f1(t)*g2(t)+f2(t)*g2(t);
(7)f(t)*δ(t)=f(t); (8)f(t)*δ(t—t0)=f(t—t0); (9)f(t)*δ’(t)=f’(t);
已知:f1(t)=e-tu(t),f2(t)=u(t)-u(t-3),求f1(t)*f2(t)。
系统如图所示,f1(t)=Sa(1000πt),f2(t)=Sa(2000πt),f(t)=f1(t)f2(t),fS(t)=f(t)p(t)。
求:系统特征方程的解
已知f1(t)=tε(t),f2(t)=ε(t)一ε(t一2),求y(t)=f1(t)*f2(t一1)*δ’(t一2)。
A./ts/,/dʒ/,/tʃ/,/tʃ/
B./tʃ/,/tʃ/,/tʃ/,/tʃ/
C./dʒ/,/tʃ/,/tʃ/,/dr/
D./tʃ/,/tʃ/,/dʒ/,/dʒ/,
若f1(t)=e-atu(t),f2(t)=sintu(t),求f1(t)*f2(t).
A.don't include
B.can't include
C.aren't included
D.haven't included