化简1-cos^4a-sin^4a/1-cos^6-sin^6a
问题描述：
化简1-cos^4a-sin^4a/1-cos^6-sin^6a
cos^6应为cos^6a
答
1-cos^6-sin^6a=1-(sin^2+cos^a)(cos^4a-cos^2asin^2a+sin^4a)=1-cos^4a+cos^2asin^2a-sin^2a=3cos^2asin^2a1-cos^4a-sin^4a=cos^2a-cos^4a+sin^2a-cos^4a=2cos^2asin^a原式=2/3