According to the plot, when [tex]t=0[/tex],
[tex]y_1(0)=a_1\sin0=0[/tex]
[tex]y_2(0)=a_2\cos0=a_2[/tex]
[tex]a_1[/tex] and [tex]a_2[/tex] are the amplitudes of the waves [tex]y_1[/tex] and [tex]y_2[/tex], respectively. From the plot it's clear that both [tex]a_1[/tex] and [tex]a_2[/tex] are positive, but the maximum value of [tex]y_2[/tex] is evidently smaller than the maximum value of [tex]y_1[/tex]. So [tex]0<a_2<a_1[/tex], making the answer B.
