※ 引述《Keyouka (初)》之銘言：
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賺 P 幣
sin(t) + cos(t) = -1/2
sin(t) * cos(t) = k/2
而 sin^2(t) + cos^2(t) = 1，上面兩式帶入得 (-1/2)^2 - 2*k/2 = 1/4 - k = 1
故 k = -3/4
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