# The radii of two concentric circles are 16 cm and 10 cm. #AB# is a diameter of the bigger circle. #BD# is tangent to the smaller circle touching it at #D#. What is the length of #AD#?

##### 2 Answers

#### Explanation:

Adopting the origin

here

Solving for

Subtracting the first from the second equation

Finally the sought distance is

or

Explanation:

If

The point

There are many ways to do that. An alternative method is

then

As per given data the above figure is drawn.

O is the common center of two concentric circles

Let

In

Applying cosine law in