sin²10°+sin²20°+sin30°+……+sin²80°=?

sin²1°+sin²2°+……sin²88°+sin²89° 证明sin(a+b)sin(a-b)=sin²a-sin² b,并用该式计算sin²20° 计算：sin²1°+sin²2°+sin²3°...+sin²45°+sin&# 数列求和 sin²1°+sin²2°+sin²3°+.+sin²88°+sin& sin²1°+sin²2°+sin²89°+sin²88°= sin²20°+sin²80°-sin20°sin80°=? 尽快 我今天将就要!化简（计算）1、Sin²10°+Sin²20°+Sin²30°+Sin 求sin²20°+sin80°sin40°,并且要用sin(α+β)sin(α-β)=sin²α-s 计算,tan91°tan92°……tan179°/sin²1°+sin²2°+……+sin² sin²40°+sin²50°+2-tan135°怎么算= sin²70°怎么化简 sin²60° 怎么算