2, 2%, -2), 2), 2], -2 ), (2), 2 ), -2, 2 +, ; -2), 2 %, π/2≤α≤π, −2), 2π], 2%), (2).........., 2}, |-2, √2, )2, -2], - 2), (2)......................, 2 =, 2 .., 2°, 2°\, =.2, - 2, (-2, 2].,  : 2, =−2, 2 ;, −2, –2, 很少说话。(2）…, 2!, √2 = ?, (2)., (2)  , (2)  , 2., - [2] - ., 2 -, 2 ............, 2........., 2) ......, 2......, 2 - ……………., 2 - ………………, 2 - ………………., 2 - ………….., 2 - ……………, 2 - …………….., – 2, 2. ........................, 2. ……………………………………………..?, (2) …………………., 2. …………….., 2..., (2) ……………………………………………………………………………………, 2. ………………………..., 2…………………………., …(2).., (2; +∞)., (2)......................................................................................................................., …(2)…, 2................................................................................................., = 2., 2................................................................................................, 2 ................................................................................................, 2 …………………………………………., 2 ................................................................., 2. ……………………………………………………………………………………., = 2, 2. ....................................................................................................................., 2. ………………………, (2) ……………………………………………………………………., (2)…………………., 2 …….………, …..× ….. 2 = ….., 2: ……………………………………………………………………………………, (2) .........................................., (2) ..............................................................................................................................., 2:, 2. ………, (2):, (2) ., (2) ;, 2) \), •2, □−2., (2) ♀  × ♂, 2 \, 2. ...................................