求证sin^2x+sin^2y-sin^2x*sin^2y+cos^2x*cos^2y=1_数学解答

求证sin^2x+sin^2y-sin^2x*sin^2y+cos^2x*cos^2y=1

人气：140 ℃　时间：2020-03-20 04:27:00

解答

sin^2x+sin^2y-sin^2x*sin^2y+cos^2x*cos^2y= sin^2x-sin^2x*sin^2y+sin^2y+cos^2x*cos^2y= sin^2x*(1-sin^2y)+sin^2y+cos^2x*cos^2y= sin^2x*cos^2y+sin^2y+cos^2x*cos^2y= sin^2x*cos^2y+cos^2x*cos^2y+sin^2y= co...