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Maths C2: Seems extremely simple but I don't get it!! watch
- Thread Starter
Last edited by TwentyTen; 12-02-2010 at 23:10.
- 12-02-2010 23:08
(Original post by TwentyTen)
- 12-02-2010 23:13
I know the principles, but I don't understand the proofs
The angle at the centre of a circle is twice the angle at the circumference.
Let angle ACO=a and angle AOX=y
Angle CAO = angle ACO (isosceles triangle)
Therefore angle CAO = a
I get that bit, this is the bit that's confusing....
Hence y= 2a (exterior angle of triangle AOC)
because the angels have equal angels they can be expressed as a but because the angle at the center is double you make it 2a=y