sin²48°+sin²42°=?

sin²1°+sin²2°+sin²89°+sin²88°= 计算：sin²1°+sin²2°+sin²3°...+sin²45°+sin&# 数列求和 sin²1°+sin²2°+sin²3°+.+sin²88°+sin& 证明sin(a+b)sin(a-b)=sin²a-sin² b,并用该式计算sin²20° sin²1°+sin²2°+……sin²88°+sin²89° 求sin²20°+sin80°sin40°,并且要用sin(α+β)sin(α-β)=sin²α-s sin²48°+sin²42°-tan²44°×tan²45°×tan² sin²20°+sin²80°-sin20°sin80°=? sin²40°+sin²50°+2-tan135°怎么算= sin²70°怎么化简 sin²60° 怎么算 尽快 我今天将就要!化简（计算）1、Sin²10°+Sin²20°+Sin²30°+Sin