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Suppose `alpha,beta,gammaa n ddelta`are the interior angles of regular pentagon, hexagon, decagon, anddodecagon, respectively, then the value of `|cosalphasecbetacosgammacos e cdelta|`is _________ |
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Answer» Correct Answer - 1 Interior angle of regular polygon of side n is `(180^(@) - (360^(@))/(n))` Hence, `alpha = 180^(@), beta = 120^(@), gamma = 144^(@), delta = 150^(@)` `:. cos alpha = cos 108^(@) = - sin 180^(@) = - ((sqrt5 -1)/(4))` `sec beta = sec 120^(@) = -2` `cos gamma = cos 144^(@) = - cos 36^(@) = - ((sqrt5 + 1)/(4))` `"cosec" delta = "cosec" 150^(@) = +2` `:. |((sqrt5 -1)/(4)) (2) ((sqrt5 +1)/(4)) (-2)| = 1` |
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