$\"\"$

\

The acceleration $\"\"$ of the spot of light is $\"\"$ .

\

$\"\"$

\

Reciprocal identity: $\"\"$ .

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

Apply Pythagorean identity: $\"\"$ .

\

$\"\"$ .

\

$\"\"$ .

\

$\"\"$

\

$\"\"$ .