x-4=5cost,y-5=5sint
(x-4)^2=25cos^2t,(y-5)^2=25sin^2t
(x-4)^2+(y-5)^2=25(cos^2t+sin^2t)
(x-4)^2+(y-5)^2=25
所以图像是一个以（4,5）为圆心,半径为5的圆