$\"\"$

\

The function is $\"\"$ on interval is $\"\"$ .

\

Number of rectangles are $\"\"$ .

\

The sum of all inscribed rectangle is lower sum.

\

$\"\"$ , where $\"\"$ .

\

The sum of all circumscribed rectangle is upper sum.

\

$\"\"$ , where $\"\"$

\

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

\

Find lower Sum.

\

$\"\"$ .

\

Area of lower sum is $\"\"$ .

\

$\"\"$

\

$\"\"$

\

Find upper Sum.

\

$\"\"$ .

\

Area of higher sum is $\"\"$

\

$\"\"$

\

$\"\"$ .

\

The function $\"\"$ on interval $\"\"$ is decreasing.

\

$\"\"$

\

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

\

Verification:

\

$\"\"$ .

\

$\"\"$

\

$\"\"$ .