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问题: 急!高中数学题

Sin^1'+sin^2'+sin^3'+sin^ 89'=?(注:其中^代表平方 '代表度)

解答:

sin^1'+sin^2'+sin^3'+...+sin^ 89'
=cos^89'+cos^88'+cos^87'+...+cos^ 1'
(sin^1'+sin^2'+sin^3'+...+sin^ 89')+(cos^89'+cos^88'+cos^87'+...+cos^ 1') =89
==> sin^1'+sin^2'+sin^3'+...+sin^ 89' =89/2