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Prove that: t a n 720^0-cos 270^0-s in 1...

Prove that: `t a n 720^0-cos 270^0-s in 150^0cos 120^0=1/4`

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` LHS =tan 720^circ-cos 270^circ-sin 150^circ cos 120^circ`
`=tan 4 pi-cos (3 pi)/2)-sin (pi-pi/6) `
`cos (pi/2+pi/6)[therefore pi=180^circ]`
`=0-0-sin (pi/6)(-sin pi/6)`
`[therefore tannpi =Oforalln in text Zandeos (3 pi)/2=0]`
`=sin ^2 pi/6`
`=(1/2)^2=1/4= RHS`
Hence proved.
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