Tangents are straight lines that touch a circle at just one spot.

This spot is called the point of tangency.

Here are some important things to know about tangents:

• A tangent line makes a right angle (90 degrees) with the radius at the point where they touch.
• If you draw two tangent lines from the same point outside the circle, those two lines will be the same length.

Here's a key idea:

If you have a point outside the circle, the lengths of the tangents to the circle—let's call them $TA$ and $TB$—are equal.

This means $TA = TB$.

This idea is really helpful when solving problems about circles and tangents in geometry.