习题解答 0.+0.0.-0 CoS 2-T sin 2a 2a 0.-0 A B0τ Sm20+τcOs20y  x o  A B  2     +    −   =  −    −  +  +   =   sin 2 cos 2 2 cos 2 sin 2 2 2 x x y x x y x y 习题解答