Viteza este: [tex]v=\pi A\cos (\pi t+\phi_0)[/tex]
Acum folosim conditiile:
[tex]y(0)=2\ \ \ \Rightarrow\ \ \ A\sin(\pi \cdot 0+\phi_0)=2\ \ \ \Rightarrow \ \ \ A\sin\phi_0=2\\ \\ v(0)=2\pi\ \ \ \Rightarrow\ \ \ \pi A\cos(\pi\cdot 0+\phi_0)=2\pi\ \ \ \Rightarrow\ \ \ A\cos\phi_0=2[/tex]
Din cele doua relatii, deducem: [tex]\sin\phi_0=\cos\phi_0[/tex] ,
de unde rezulta ca:
[tex]\phi_0=\dfrac{\pi}{4}.[/tex]
