# Crossing Chords: Proof Hint

- Author:
- Tim Brzezinski

- Topic:
- Angles, Circle, Similar Triangles, Triangles

In the applet below, 2 intersecting chords are drawn within a circle.
Interact with the applet below for a few minutes, then answer the questions that follow.

## 1.

What do you know about the measures of the **pink angles**?

## 2.

Why is your response to (1) true?

## 3.

What do you know about the measures of the **blue angles**? Why is this?

## 4.

Given your responses to (1) & (3) what can you conclude about the two triangles?

## 5.

Use your response to (4) to write a relationship (equation) among the lengths a, b, c, and d.

## 6.

Rewrite your equation in (5) above so that both sides of the equation are written as products instead of ratios. What do you get?