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October 21, 2025, 08:41:04 pm
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Author Topic: Q  (Read 1301 times)  Share 

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TonyHem

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Q
« on: July 23, 2009, 12:27:31 am »
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This diagram shows a circle with center O. Two tangles of the circle intersect at B and intersect the circle at A and C. The angle <CDA is 70degrees. The angle <CBA is?

edit: that dot I put in the picture is the center
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TrueTears

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Re: Q
« Reply #1 on: July 23, 2009, 12:33:17 am »
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1. You can either use alternate segment theorem

or

2. 2 tangents from a single point to a circle is equal in length so it is an isosceles triangle.
« Last Edit: July 23, 2009, 04:20:27 pm by TrueTears »
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kamil9876

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Re: Q
« Reply #2 on: July 23, 2009, 12:49:44 am »
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Let O be the centre. You can just draw in lines CO and AO and you get the quadrilateral OCBA. Now the sum of the angles of this shape is 360 hence:




Now using this well known geometry theorem you can work out that:

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TonyHem

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Re: Q
« Reply #3 on: July 23, 2009, 12:59:27 am »
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I don't remember covering this :S
Think I got it now,thanks for the help!  :)
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TrueTears

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Re: Q
« Reply #4 on: July 23, 2009, 04:20:44 pm »
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Quote from: TonyHem on July 23, 2009, 12:59:27 am
I don't remember covering this :S
Think I got it now,thanks for the help!  :)
I believe this was meant to be covered in General maths.
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PhD @ MIT (Economics).

Interested in asset pricing, econometrics, and social choice theory.
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