sum sin mat sumsin( t)=sin( 3t)+sin(0. 3t)+sin(0.03t) fregbrk.mat fregbrk(t sin(0.03)1≤t<500 S(0.37)501≤t≤1000       = = + + sin( 0.3 ) 501 1000 sin( 0.03 ) 1 500 ( ) . sin( ) sin( 3 ) sin( 0.3 ) sin( 0.03 ) sin . t t t t freqbrk t freqbrk mat sum t t t t sum mat