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**tony123****Member**- Registered: 2007-08-03
- Posts: 197

In triangle ABC where AB=4,BC=5,AC=6 Prove that cos 2C=cos B

*Last edited by tony123 (2018-11-23 03:37:28)*

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**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,462

Hi Tony123

I used the cosine rule thus:

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Sometimes I deliberately make mistakes, just to test you! …………….Bob Bundy

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