△=b^2-4ac=64(sinxy)^2-64≥0 故sinxy=1或-1 xy=kπ+π/2
方程为x^2+8x+16=0或x^2-8x+16=0 x=4或-4
x=4 xy=π/2,3π/2,5π/2,7π/2...15π/2共8组
x=-4,也是8组 合计实数对(x.y)的个数为16
△=b^2-4ac=64(sinxy)^2-64≥0 故sinxy=1或-1 xy=kπ+π/2
方程为x^2+8x+16=0或x^2-8x+16=0 x=4或-4
x=4 xy=π/2,3π/2,5π/2,7π/2...15π/2共8组
x=-4,也是8组 合计实数对(x.y)的个数为16