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os)2cos (s i n)2s i n (????????????s i n)23c o s (c o s)23s i n (???????????s i n)23c o s (c o)23s i n (????????????s i n)2c o s (c o s)2s i n (???????????s i n)2cos (cos)2s i n (??????yx 共同點(diǎn): 函數(shù)名改變 ,符號(hào)與 前面值 的正負(fù)一至 . ※ 記憶方法: 奇變偶不變,符號(hào)看象限. 說明: )(2由象限決定數(shù)的符號(hào)符號(hào)指的是前面三角函的奇偶性;中奇偶指的是 kk?牛刀小試 ???? )3c os (,31)6s i n (:1 ???????? )4s i n (,31)4c os (:2 ????挖掘角的相互關(guān)系,尋求誘導(dǎo)公式的應(yīng)用 互余關(guān)系 變式練習(xí): ??????)32s i n (232,31)6c o s (??????? ,則牛刀小試 ???? )65s i n (,31)6s i n (:3 ???????? )65c os (,31)6c os (:4 ????挖掘角的相互關(guān)系,尋求誘導(dǎo)公式的應(yīng)用 互補(bǔ)關(guān)系 等于)2s i n (?? ?牛刀小試 )2s i n (.)2c os (.)2c os (.)23s i n (.????????????DCBA A牛刀小試 的值是則在第四象限,)23s i n (54)2c os (????????54.53.53.53. DCBA ??A牛刀小試 等于則 ?? 10c o s,280s i n m?221:1:::mDmCmBmA???? B牛刀小試 ???? )22c os ()22s i n (21??2co s2s i n ?牛刀小試 求下式的值,3)t a n ( ?? ??)c os ()s i n ()2c os ()2s i n (??????????????)c o s ()s i n ( ???? ??)29s i n ()s i n ()3s i n ()c os ()211c os ()2c os ()c os ()2s i n (:1?????????????????????????化簡能力提升 )c o s ()23c o s ()23