If the angles A, B of triangle ABC are such that and , find without using tables the value of Cos C'

Thanks.

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- Feb 20th 2010, 03:47 PMdeltaxraysums and differences of angles
If the angles A, B of triangle ABC are such that and , find without using tables the value of Cos C'

Thanks. - Feb 20th 2010, 03:53 PMicemanfan

Using identities:

You should be able to calculate and .