a) 

$$x_M = IA \cdot \cos(\alpha)$$

$$x_M = 8 \cos(\alpha) \quad (\text{cm})$$

b) 

Ta có: $x_M(t) = 8 \cos(\omega t)$

Tại $t = 1$ phút:

    $$x_M(1) = 8 \cos(\omega) = -3 \implies \cos(\omega) = -\frac{3}{8}$$

Tại $t = 2$ phút:

    $$x_M(2) = 8 \cos(2\omega)$$

     $\cos(2\omega) = 2\cos^2(\omega) - 1$:

    $$x_M(2) = 8 \left( 2\cos^2(\omega) - 1 \right)$$

    $$x_M(2) = 8 \left( 2 \left(-\frac{3}{8}\right)^2 - 1 \right)$$

    $$x_M(2) = 8 \left( 2 \cdot \frac{9}{64} - 1 \right)$$

    $$x_M(2) = 8 \left( \frac{18}{64} - \frac{64}{64} \right)$$

    $$x_M(2) = 8 \left( -\frac{46}{64} \right) = 8 \left( -\frac{23}{32} \right)$$

    $$x_M(2) = -\frac{23}{4} = -5.75$$

    $$x_M(2) \approx -5.8 \quad (\text{cm})$$