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If A ,\ B ,\ C ,\ D are angles of a cycl...

If `A ,\ B ,\ C ,\ D` are angles of a cyclic quadrilateral, prove that `cos A+cos B+cos C+cos D=0.`

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As the quadrilateral ABCD is cyclic in nature,
`A + C = 180° and B +D = 180°`
Hence, `Cos A = Cos (180° – C) = -Cos C … (1)`
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