已知tana=2,求2/3sin^2a+1/4cos^2a的值!請(qǐng)高手作出詳細(xì)過程!
熱心網(wǎng)友
因?yàn)橛晒?cos^2a=1/1+tan^2a 可得cos^2a=1/5原式=cos^2a(2/3tan^2a+1/4) =1/5(8/3+1/4) =7/12
熱心網(wǎng)友
cos2a=1-tan^a/1+tan^a=-3/5sina2a=4/5代入原式=31/60
已知tana=2,求2/3sin^2a+1/4cos^2a的值!請(qǐng)高手作出詳細(xì)過程!
因?yàn)橛晒?cos^2a=1/1+tan^2a 可得cos^2a=1/5原式=cos^2a(2/3tan^2a+1/4) =1/5(8/3+1/4) =7/12
cos2a=1-tan^a/1+tan^a=-3/5sina2a=4/5代入原式=31/60