Áp dụng công thức: \(A^2=x^2+\frac{v^2}{\omega^2}\)
với \(x=\frac{A}{2}\) ta có
\(A^2=\left(\frac{A}{2}\right)^2+\frac{v^2}{\omega^2}\Leftrightarrow\frac{3A^2}{4}=\frac{v^2}{\omega^2}\Leftrightarrow v^2=\frac{3A^2}{4}.\omega^2\Rightarrow \left|v\right|=\frac{\sqrt{3}A}{2}.\omega=\frac{\sqrt{3}A}{2}.\frac{2\pi}{T}\)