【正文】
71tan1 1tan)45t a n(,34c oss i ntan ?? ????? ???????? 例 2. .10t an3150s i n )(利用三角公式化簡 ??? 解: )(原式 ? ???? 10c os 10s in3150s in ???????10c o s)10s i n2310c o s21(250s i n ? ???????? 10c os 10s i n30c os10c os30s i n50s i n2 ????? 10cos 40sin40cos2