若sinxsiny=1,则cos(x+y)的值为

你好,解答如下：因为sinxsiny = 1所以sinx = 1,siny = 1或者sinx = -1,siny = -1不管为哪种情况,都有cosx = cosy = 0所以cos（x + y）=cosxcosy - sinxsiny = 0 - 1 = -1...