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Prove that cos^(2)40^(@)cos^(2)80^(@)+co...

Prove that `cos^(2)40^(@)cos^(2)80^(@)+cos^(2)80^(@)cos^(2)20^(@)+cos^(2)200^(@)cos^(2)40^(@)=(17)/(16)`

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CHHAYA PUBLICATION-MISCELLANEOUS EXAMPLES-TRIGONOMETRY
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