1、已知sinx^4+cosx^4=5/9,求sin2x的值 2、已知cos2x=3/5,求sinx^4+cosx^4
来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/05/13 20:07:32
1、已知sinx^4+cosx^4=5/9,求sin2x的值 2、已知cos2x=3/5,求sinx^4+cosx^4
(sinx)^2 +(cosx)^2 =1 两边平方(sinx)^4 +(cosx)^4 +2(sinx)^2(cosx)^2 =1
=> 5/9+2(sinx)^2(cosx)^2 =1 => (sinx)^2(cosx)^2 =2/9
sin2x =2sinxcosx => (sin2x)^2=4(sinx)^2(cosx)^2=8/9 => sin2x=±2√2 / 3 .(1)
(sinx)^4 +(cosx)^4 =1-2(sinx)^2(cosx)^2 =1- 0.5(sin2x)^2...(*)
cos2x=3/5 => sin2x=±4/5 代入(*) => 1-0.5*(±0.8)^2=0.68...(2)
=> 5/9+2(sinx)^2(cosx)^2 =1 => (sinx)^2(cosx)^2 =2/9
sin2x =2sinxcosx => (sin2x)^2=4(sinx)^2(cosx)^2=8/9 => sin2x=±2√2 / 3 .(1)
(sinx)^4 +(cosx)^4 =1-2(sinx)^2(cosx)^2 =1- 0.5(sin2x)^2...(*)
cos2x=3/5 => sin2x=±4/5 代入(*) => 1-0.5*(±0.8)^2=0.68...(2)
1、已知sinx^4+cosx^4=5/9,求sin2x的值 2、已知cos2x=3/5,求sinx^4+cosx^4
sinx+cosx=1/5,x属于(π/2,3π/4),求sinxcosx,sin2x,cos2x,sinx,cosx
(1)已知:(4sinx-2cosx)/(5cosx+3sinx)=6/11 求sinx乘以cosx的值
已知cos2x=3/5,求sinx^4+cosx^4
已知sinx=-1/2cosx,cosx-sinx/cosx+sinx+sin2x+cos2x的值
:已知(sinx+cosx)/(sinx-cosx)=3,求tanx,2sin2x+(sinx-cosx)2的值.
已知sin2x=tanx-cos2x 求sinx-cosx的值
已知x∈(0,π),且sinx+cosx=1/2 求sin2x+cos2x,sinx-cosx的值
已知2sin2x-cos2x+sinxcosx-6sinx+3cosx=0,求2cosx(sinx+cosx)1+tan
已知4sinx^2-cosx^2-6sinx+3cosx=0,求(cos2x-cosx^2)/(1-cotx^2)的值
已知tan(x+5π/4)=2 (1)求tanx的值(2)求sinx+cosx/sinx-cosx +sin2x+cos
已知1+sinx+cosx+sin2x+cos2x=0,求tanx