sin 15°49′=?

sin 15°49′=? sin(10°)+sin(50°)-sin(70°) =sin(10°)+sin(50°)-sin(70°) = sin(a-15)=-sin(15-a)? cos^15°-sin^15°= 计算：sin(15°）=? sin(π/3+15°)= sin 15°是多少 函数y=sin(x+15°)+sin(x+75°)的最大值 计算:sin方10°+sin方20°+sin方30°+sin方40°+sin方50°+sin方60°+sin方70°+sin方80°+sin方90°= sin²1°+sin²2°+sin²3°+……+sin²87°+sin²88°+sin²89°= sin²1°+sin²2°+sin²3°+...+sin²88°+sin²89°+sin²90°=等于多少? 为什么sin（-261°)=sin（-261°+360°) sin²15° 把sin变成带cos的 sin²48°+sin²42°=? 证明：sin(360°-α)=-sinα sin²120°= sin(a+360°)=? sin(-15度)=什么?