help appreciated

Printable View

- Dec 8th 2008, 05:20 AMhelloyingangles in circle
help appreciated

- Dec 8th 2008, 06:43 AMGrandadAngles in circles
Hi -

You need to use the most important fact about angles in circles, which is:

- The angle subtended at the centre of a circle is twice the angle subtended at a point on the circumference by the same arc.

But you do need to understand what 'subtended' means.

In your diagram, look at the arc AE. The angle it*subtends*at the centre is angle AOE (the one we want in part (a)) and the angle it*subtends*at the circumference is angle ACE (which is 31 degrees). So angle AOE is twice angle ACE.

For part (b) use the fact that the angles on the straight line BOD add up to 180 degrees.

Hope you can do it now.

Grandad - Dec 8th 2008, 06:47 AMsamer_guirguis_2000
It is very easy if you can just multiply by two.