已知tanα+1/tanα=5/2,求2sin2(3π-α)-3cos(π/2+α)sin(3π/2-α)的值

来源:学生作业帮助网 编辑:作业帮 时间:2024/11/24 17:06:11
已知tanα+1/tanα=5/2,求2sin2(3π-α)-3cos(π/2+α)sin(3π/2-α)的值
x){}KKm6ӶF:66gio=QS89X|6Ijyڰ&HPu@cA48#&8Dd OM5R@PaC__9R0 ANG8*lhoj_\g /ֱW

已知tanα+1/tanα=5/2,求2sin2(3π-α)-3cos(π/2+α)sin(3π/2-α)的值
已知tanα+1/tanα=5/2,求2sin2(3π-α)-3cos(π/2+α)sin(3π/2-α)的值

已知tanα+1/tanα=5/2,求2sin2(3π-α)-3cos(π/2+α)sin(3π/2-α)的值
tana+1/tana=5/2
(tan^2a+1)/tana=5/2
2sin2(3π-a)-3cos(π/2+a)sin(3π/2-a)
=-2sin2a-3sinacosa
=-4sinacosa-3sinacosa
=-7sinacosa
=-7sinacosa/(sin^2a+cos^2a)
=-7tana/(tan^2a+1)
=-14/5