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Let-d-n-be-the-determinant-of-the-n-n-matrix-whose-entries-from-left-to-right-and-then-from-top-to-bottom-are-cos-1-cos-2-cos-n-2-For-example-d-3-determinant-cos-1-cos-2-cos-3-




Question Number 68782 by Maclaurin Stickker last updated on 06/Oct/19
Let d_n  be the determinant of the n×n  matrix whose entries, from left to right  and then from top to bottom, are  cos 1, cos 2, ..., cos n^2 . (For example,  d_3 = determinant (((cos 1  cos 2  cos 3)),((cos 4  cos 5  cos 6)),((cos 7  cos 8  cos 9))).  The argument of cos is always in radians  not degrees.)   Evalue lim_(n→∞)  d_(n.)
$$\mathrm{Let}\:{d}_{{n}} \:\mathrm{be}\:\mathrm{the}\:\mathrm{determinant}\:\mathrm{of}\:\mathrm{the}\:{n}×{n} \\ $$$$\mathrm{matrix}\:\mathrm{whose}\:\mathrm{entries},\:\mathrm{from}\:\mathrm{left}\:\mathrm{to}\:\mathrm{right} \\ $$$$\mathrm{and}\:\mathrm{then}\:\mathrm{from}\:\mathrm{top}\:\mathrm{to}\:\mathrm{bottom},\:\mathrm{are} \\ $$$${cos}\:\mathrm{1},\:{cos}\:\mathrm{2},\:…,\:{cos}\:{n}^{\mathrm{2}} .\:\left(\mathrm{For}\:\mathrm{example},\right. \\ $$$${d}_{\mathrm{3}} =\begin{vmatrix}{{cos}\:\mathrm{1}\:\:{cos}\:\mathrm{2}\:\:{cos}\:\mathrm{3}}\\{{cos}\:\mathrm{4}\:\:{cos}\:\mathrm{5}\:\:{cos}\:\mathrm{6}}\\{{cos}\:\mathrm{7}\:\:{cos}\:\mathrm{8}\:\:{cos}\:\mathrm{9}}\end{vmatrix}. \\ $$$$\mathrm{The}\:\mathrm{argument}\:\mathrm{of}\:{cos}\:\mathrm{is}\:\mathrm{always}\:\mathrm{in}\:\mathrm{radians} \\ $$$$\left.\mathrm{not}\:\mathrm{degrees}.\right)\: \\ $$$$\mathrm{Evalue}\:\underset{{n}\rightarrow\infty} {\mathrm{lim}}\:{d}_{{n}.} \\ $$

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