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Prove that: cos 78^0cos 42^0cos 36^0=1/8...

Prove that: `cos 78^0cos 42^0cos 36^0=1/8`

Text Solution

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Let us consider the LHS

`cos 78° cos 42° cos 36°`

Now let us multiply and divide by 2 we get,

`cos 78° cos 42° cos 36° = 1/2 (2 cos 78° cos 42° cos 36°)`

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