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The value of `[ ( sin ""(pi)/(9)) (4+ sec""(pi)/(9))]^(2)` is _______. |
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Answer» Correct Answer - 3 `(sin ""(pi)/(9)) (4+sec""(pi)/(9))` ` " " = sin 20^(@) ( 4+ (1)/( cos 20^(@)))` ` " " = ( 4 sin 20^(@) cos 20^(@) + sin 20^(@))/( cos 20^(@))` `" " = ( 2 sin 40^(@) + sin 20^(@))/( cos 20^(@))` `" " = (sin 40^(@) + ( sin 40^(@) + sin 20^(@))/(cos 20^(@))` ` ( sin 40^(@) + 2 sin 30^(@) cos 10^(@))/(cos 20^(@))` `= ( sin 40^(@) + cos 10^(@))/( cos 20^(@))` `= (cos 50^(@) + cos 10^(@))/(cos 20^(@))` `= ( 2 cos 30^(@) cos 20^(@))/(cos 20^(@))` ` = sqrt3` |
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