1.

The value of `(sin12^(@)xxcos18^(@)xxsec78^(@)xxcosec72^(@))` is _______

Answer» We have, `sin12^(@)xxcos18^(@)xxsec78^(@)xxcosec72^(@)`
`=sin12^(@)xxcos18^(@)xxsec(90^(@)-12^(@))xxcosec(90^(@)xx18^(@))`
`=sin12^(@)xxcos18^(@)xx(1)/(sin12^(@))=1xx1=1`.


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