$\"\"$

\

The functions are $\"\"$ , $\"\"$ when $\"\"$ .

\

Consider $\"\"$ .

\

Substitute $\"\"$ in $\"\"$ .

\

Then $\"\"$ .

\

Differentiate x with respect to s.

\

$\"\"$ .

\

Differentiate x with respect to t.

\

$\"\"$ .

\

Differentiate x with respect to u.

\

$\"\"$

\

$\"\"$

\

Consider $\"\"$ .

\

Substitute $\"\"$ in $\"\"$ .

\

$\"\"$

\

Differentiate y with respect to s.

\

$\"\"$

\

Substitute $\"\"$ in $\"\"$ .

\

$\"\"$

\

Differentiate y with respect to t.

\

$\"\"$

\

Substitute $\"\"$ in $\"\"$ .

\

$\"\"$

\

Differentiate x with respect to u.

\

$\"\"$

\

Substitute $\"\"$ in $\"\"$ .

\

$\"\"$

\

$\"\"$ $\"\"$ .

\

Differentiate z with respect to x.

\

$\"\"$

\

Substitute $\"\"$ in $\"\"$ .

\

$\"\"$

\

Differentiate z with respect to y.

\

$\"\"$

\

Substitute $\"\"$ in $\"\"$ .

\

$\"\"$

\

$\"\"$

\

Find $\"\"$ .

\

Use chain rule : $\"\"$ .

\

$\"\"$

\

$\"\"$

\

Find $\"\"$ .

\

Use chain rule : $\"\"$ .

\

$\"\"$

\

$\"\"$

\

Find $\"\"$ .

\

Use chain rule : $\"\"$ .

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$ , $\"\"$ and $\"\"$ .