Verified Answer :

y = A cos (B(x - C) + D

A gives the amplitude, which is the maximum displacement, so it's 9.

Answer:

The maximum displacement from the equilibrium position is 9.

Step-by-step explanation:

The given simple harmonic motion is:

\(d=9cos(\frac{\pi}{2}t)\)

Differentiating above equation with respect to t, we get

\(d'=-9sin(\frac{\pi}{2}t)(\frac{\pi}{2})\)

⇒\(d'=-\frac{9{\pi}}{2}sin(\frac{\pi}{2}t)\)

Again differentiating the above equation with respect to t, we have

\(d''=-\frac{9({\pi})^{2}}{4}cos(\frac{\pi}{2}t)<0\)

Now, \(d'=0\)

⇒\(-\frac{9{\pi}}{2}sin(\frac{\pi}{2}t)=0\)

⇒\(sin(\frac{\pi}{2}t)=0\)

⇒\(\frac{\pi}{2}t=0\)

⇒\(t=0\)

Substituting the value of t=0 in d, we get

⇒\(d=9cos(\frac{\pi}{2}(0))\)

⇒\(d=9cos(0)\)

⇒\(d=9(1)\)

⇒\(d=9\)

Therefore, the maximum displacement from the equilibrium position is d= 9.