中四maths一條

樓上第二步o個度錯左。(1+cos2x)應該係 = (2-sin2x)，你冇左個2字。
圖片參考：http://i169.photobucket.com/albums/u209/lautszki/tri-sim.jpg

我認為E個答案以經係最簡啦
如果有人可以再簡，歡迎再答

(sin^2 x)/(1+cos^2 x) -tan^2 x
= sin^2/(-sin^2x) - tan^2x
= -1 - tan^2x
= - cos^2x/cos^2x - tan^2x cos^2x/ cos^2x
= - cos^2x - sin^2x/ cos^2x
= - (cos^2x + sin^2x) / cos^2x
= -1/con^2x