Circle Geometry in 2U HSC Paper? (1 Viewer)

[paddy86]

Question 9. (b) of HSC 2003 paper.

I noticed to find the angle to solve (iii) you need to use the double-angle rule (in a circle the angle at the center is double of the angle at the circumference, when the angles have the same circumference as base) which I faintly remembered back from year 10.

Should we that only do 2U familiarise with other circle geometry rules?

 

[Trebla]

You don't need to know any circle geometry theorems as they are exclusively Extension level material. Angle BOC can be found without any application of circle geometry theorems.

We found angle BAO = 30º from (i), now angle ABO = 30º by isosceles triangle AOB, hence angle AOB = 120º. By congruent triangles angle AOC = 120º, thus angle BOC = 120º by angles at a point...notice we haven't used any circle geometry theorems at all.

 

[khorne]

The only reason they put it in a circle, is because you can use the fact that radii are equal.

 

[x_symphonic]

circle geometry is pure 3u. This question is based on 2u knowledge of circles