# Angle In A Circle 1

## Inscribe Angle and Central Angle

ACB is called central angle or angle at the centre subtended arc AB. ADB is called inscribed angle or angle at the circumference subtended arc AB. Do the following instruction and try to answer the question!

## 1. Inscribed Angle

Move point D along arc AB, then pay attention to ADB. What do you think about ADB when you move point D? (Note : Move the points A or/and B to change the angle)

## 2. Central Angle

Move points A and B, then pay attention to ACB and the measure of arc AB. What do you think about the measure of ACB and arc AB when you move points A and B?

## 3. Relation Of Central Angle and Inscribed Angel

Move points A and B, then pay attention to ACB and ADB. What do you think about the relation of ACB and ADB measurement values? (Hint : Try to add, subtract, times or divide both angles for several different measurement value, and write your discovery result as the answer.)

## 4. Conclution

Write your conclusions based your discovery result, and discuss with your workgroup to complete the group report!