A circle of radius 8 is externally tangent to a circle of radius 18...?

Question

Find the length of a common external tangel segment. (You need to find the length of AB)
For the image please go to: http://i3.tinypic.com/2u6ocus.jpg......
Please help, I've been trying to figure this out for the past hour.

Answer 1

Draw a radius in each circle going to the respective points of tangency. These make right angles with the tangent (radii are perpendicular to a tangent at their point of tangency).

Then draw a segment parallel to the tangent line from the center of the smaller circle, intersecting the radius of the larger that you just drew. This makes a rectangle and a right triangle. The segment is equal in length to the tangent segment, but is also a leg of a right triangle with other leg = (18-8) =10 and hypotenuse 18. Use Pythagorean Theorem to find it. Hope that helps!

Answer 2

26