Đáp án:
$\begin{align}
& 1)A=25{{\pi }^{2}}cm;\omega =5\pi (rad/s);\varphi =-\dfrac{\pi }{2} \\
& T=\dfrac{2\pi }{\omega }=0,4s;f=\dfrac{1}{T}=2,5Hz \\
\end{align}$
$\begin{align}
& 2)A=50{{\pi }^{2}}cm;\omega =5\pi (rad/s);\varphi =\dfrac{5\pi }{6} \\
& T=\dfrac{2\pi }{\omega }=0,4s;f=\dfrac{1}{T}=2,5Hz \\
\end{align}$
Giải thích các bước giải:
$\begin{align}
& x=-25{{\pi }^{2}}cos(5\pi t+\dfrac{\pi }{2})cm/{{s}^{2}} \\
& x=-50{{\pi }^{2}}\sin (5\pi t+\dfrac{\pi }{3})cm/{{s}^{2}} \\
\end{align}$
1.
$\begin{align}
& x=-25{{\pi }^{2}}cos(5\pi t+\dfrac{\pi }{2})cm/{{s}^{2}} \\
& =25{{\pi }^{2}}cos(5\pi t+\dfrac{\pi }{2}+\pi ) \\
& =25{{\pi }^{2}}cos(5\pi t-\dfrac{\pi }{2}) \\
& \Rightarrow A=25{{\pi }^{2}}cm;\omega =5\pi (rad/s);\varphi =-\dfrac{\pi }{2} \\
& T=\dfrac{2\pi }{\omega }=0,4s; \\
& f=\dfrac{1}{T}=2,5Hz \\
\end{align}$
$\begin{align}
& 2>x=-50{{\pi }^{2}}\sin (5\pi t+\dfrac{\pi }{3})cm/{{s}^{2}} \\
& =50{{\pi }^{2}}cos(5\pi t+\dfrac{\pi }{3}+\dfrac{\pi }{2}) \\
& =50{{\pi }^{2}}cos(5\pi t+\dfrac{5\pi }{6}) \\
& \Rightarrow A=50{{\pi }^{2}}cm;\omega =5\pi (rad/s);\varphi =\dfrac{5\pi }{6} \\
& T=\dfrac{2\pi }{\omega }=0,4s;f=\dfrac{1}{T}=2,5Hz \\
& x=-50{{\pi }^{2}}\sin (5\pi t+\dfrac{\pi }{3})cm/{{s}^{2}} \\
\end{align}$
