Figure shows the circular motion of a particle. The radius of the c...

Figure shows the circular motion of a particle. The radius of the circle, the period, sense of revolution and the initial position are indicated on the figure. The simple harmonic motion of the \( \mathrm{x} \)-projection of the radius vector of the rotating particle \( \mathrm{P} \) is:
a. \( x(t)=B \sin \left(\frac{2 \pi t}{30}\right) \)
b. \( x(t)=B \cos \left(\frac{\pi t}{15}\right) \)
c. \( x(t)=B \sin \left(\frac{\pi t}{15}+\frac{\pi}{2}\right) \)
d. \( x(t)=B \cos \left(\frac{\pi t}{15}+\frac{\pi}{2}\right) \)