sinX+cosX=5/6
求(1)sin2X
(2)cos2X
這題三角函數怎麼算??速速求解阿~~~?
2015-11-17 3:45 pm
回答 (1)
2016-01-26 2:23 pm
sin x+cos x=5/6
(sin x)^2 +2(sin x)(cos x)+ (cos x)^2=25/36
1+sin(2x)=25/36
sin(2x)=-11/36
cos(2x)={1-[sin (2x)]^2}^0.5
cos(2x)=(1-121/1296)^0.5
cos(2x)=(1175/1296)^0.5
(sin x)^2 +2(sin x)(cos x)+ (cos x)^2=25/36
1+sin(2x)=25/36
sin(2x)=-11/36
cos(2x)={1-[sin (2x)]^2}^0.5
cos(2x)=(1-121/1296)^0.5
cos(2x)=(1175/1296)^0.5
收錄日期: 2021-04-18 14:03:40
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20151117074551AAighb7