证明：输入过于麻烦,用换元法吧设A=sin²A,B=sin²B∵ sin^4a/sin^2b+cos^4a/cos^2b=1即A²/B+(1-A)²/(1-B)=1∴ A²(1-B)+(1-A)²B=B(1-B)∴ A²-A²B+B-2AB+A²B=B-B²∴...