$\"\"$

Let $\"\"$ and D be a point on the given circle is $\"\"$ .

Find $\"\"$ first.

$\"\"$ (Apply Secant theorem)

$\"\"$ ( $\"\"$ )

$\"\"$ (Substitute $\"\"$ )

$\"\"$ (Subtract: $\"\"$ )

$\"\"$ (Divide: $\"\"$ ) $\"\"$

The value of $\"\"$ .