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Angles in a Circle
1/6
Must Do·26/31 papers · 6 years
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By the end of this lesson, you'll solve:

"If you draw a triangle inside a semicircle with one side as the diameter, what is the angle opposite the diameter? Always!"

Central Angle: The Boss Angle

Picture this: you slice a pizza from the center -- the angle at the tip is a central angle. It sits at the center of the circle, made by two radii.

O120°60°● Central angle● Inscribed angle = half
Central120°
Central120°
Inscribed60°

Key Points

  • 1
    Vertex is at the center of the circle
  • 2
    The arc it cuts off = intercepted arc
  • 3
    Central angle = intercepted arc (in degrees)
  • 4
    Full circle = 360 degrees

Pro Tip

4 equal pizza slices = 360/4 = 90 degrees each.

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