\

\

Given

\

$\"image\"$

\

squaring on each side

\

$\"image\"$

\

from formula

\

$\"image\"$

\

we can write

\

$\"image\"$

\

$\"image\"$

\

(since)

\

$\"image\"$

\

$\"image\"$

\

We have fomula

\

$\"image\"$

\

here

\

$\"image\"$

\

substitute in formula

\

$\"image\"$

\

$\"image\"$

\

$\"image\"$

\

$\"image\"$

\

$\"image\"$

\

substract trems of \ \

\

$\"image\"$

\

$\"image\"$

\

Take out common factor 2

\

$\"image\"$

\

We know that

\

$\"image\"$

\

$\"image\"$

\

Squaring on each side

\

$\"image\"$

\

Hence it is proved that

\

$\"image\"$

\

\