Circle theorems are generally quite hard to master as they compose of 9 rules that you have to learn in order to answer the questions successfully.
Knowing the circle- the different parts you need to be familiar with.
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rule 1: The angle at the centre of the circle is twice as big as the angle at the circumference.
rule 2: The angle in a semi-circle is 90 degrees.
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Rule 3: A tangent meets a radius at 90 degrees
rule 4: Two radius meet at a chord to make an isosceles triangle.
rule 5: Angles in the same segment are the same.
rule 6: Opposite angles in a cyclic quadrilateral add to 180 degrees.
rule 7: The perpendicular chord bisector is a diameter.
rule 8: Tangents that meet at the same point are equal.
rule 9: Angles in the alternate segment are equal.
I hope this was useful to you.
Hope everyone has a great weekend. :)
Jonathan