Let `z=(cosx)^5 and y="sin"xdot` Then the value of `(d^2z)/(dy^2)a tx=(2pi)/9` is____________.

Explanation

To solve the problem step by step, we start with the given functions and apply differentiation accordingly.

### Step 1: Define the functions
Let \( z = (\cos x)^5 \) and \( y = \sin x \).

### Step 2: Differentiate \( z \) with respect to \( x \)
Using the chain rule and the power rule:
\[
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