Area of Trapezia and Circles

• Radius- the distance from the centre to the circumference. It can go in any direction
• Diameter- the distance from one side of the circle to the other, passing through the centre. It is double the length of the radius
• Circumference- the distance all the way around the circle( basically the perimeter)
• The diameter, radius and circumference

  
• Formula for the circumference- πd/ πxrxr.

  This is the perimeter of a circle.
• Area of a circle- πr²
• Area of a semicircle


  πr² ÷2
• How to work out the area of a circle without a circle:

  Radius=9

  πr²

  π9²

  π81---- 81πcm²= final answer

  You would divide that by 2 to find the area of a semicircle and by 4 to find a 1/4 of a circle