cos100°=k
cos80°=cos(180°-100°）=-cos100°=-k
sin²80°=1-cos²80°=1-k²
sin80°>0
sin80°=√(1-k²）
tan80°=sin80°/cos80°=-√(1-k²)/k
cos100度=k,则tan80度=多少
cos100°=k
cos80°=cos(180°-100°）=-cos100°=-k
sin²80°=1-cos²80°=1-k²
sin80°>0
sin80°=√(1-k²）
tan80°=sin80°/cos80°=-√(1-k²)/k