如图所示,22题怎么写啊?如果有空.把第23题也告诉我把···
来源:学生作业帮 编辑:搜狗做题网作业帮 分类:数学作业 时间:2024/08/16 05:03:33
如图所示,22题怎么写啊?如果有空.把第23题也告诉我把···
如下图所示,忘记插图了···嘿嘿
![](http://img.wesiedu.com/upload/7/08/70825e8d017d3edd1b560ba8bc4b3b44.jpg)
如下图所示,忘记插图了···嘿嘿
![](http://img.wesiedu.com/upload/7/08/70825e8d017d3edd1b560ba8bc4b3b44.jpg)
![如图所示,22题怎么写啊?如果有空.把第23题也告诉我把···](/uploads/image/z/17951432-32-2.jpg?t=%E5%A6%82%E5%9B%BE%E6%89%80%E7%A4%BA%2C22%E9%A2%98%E6%80%8E%E4%B9%88%E5%86%99%E5%95%8A%3F%E5%A6%82%E6%9E%9C%E6%9C%89%E7%A9%BA.%E6%8A%8A%E7%AC%AC23%E9%A2%98%E4%B9%9F%E5%91%8A%E8%AF%89%E6%88%91%E6%8A%8A%C2%B7%C2%B7%C2%B7)
22.1)a*b=√2(cosx+sinx)=(1/2)sin(x+π/4)=8/5
sin(x+π/4)=4/5 x∈(π/4,π/2)
∴cos(x+π/4)=-3/5
sin(x-π/4)=sin(x+π/4-π/2)
=-cos(x+π/4)
=3/5
cos(x-π/4)=cos(x+π/4-π/2)
=sin(x+π/4)
=4/5
tan(x-π/4)=(3/5)/(4/5)=3/4
2)a*b=√2(cosx+sinx)=8/5
cosx+sinx=4√2/5 两边平方:1+sin2x=32/25
∴ sin2x=7/25 2x∈(π/2,π)
cos2x=-24/25
sin2x(1+tanx)/(1-tanx)=sin2x(cosx+sinx)/(cosx-sinx)
=sin2x(1+sin2x)/cos2x
=-28/75
23.做CD⊥AB,D为垂足
acosB=BD=3 bsinA=CD=4
a^2=BD^2+CD^2=25 ∴ a=5
S=AB*CD/2=(BD+AD)CD/2=10
[3+√(b^2-16)]4/2=10 b=2√5
c=AB=3+√(b^2-16)=5或1
l=a+b+c=10+2√5或6+2√5
sin(x+π/4)=4/5 x∈(π/4,π/2)
∴cos(x+π/4)=-3/5
sin(x-π/4)=sin(x+π/4-π/2)
=-cos(x+π/4)
=3/5
cos(x-π/4)=cos(x+π/4-π/2)
=sin(x+π/4)
=4/5
tan(x-π/4)=(3/5)/(4/5)=3/4
2)a*b=√2(cosx+sinx)=8/5
cosx+sinx=4√2/5 两边平方:1+sin2x=32/25
∴ sin2x=7/25 2x∈(π/2,π)
cos2x=-24/25
sin2x(1+tanx)/(1-tanx)=sin2x(cosx+sinx)/(cosx-sinx)
=sin2x(1+sin2x)/cos2x
=-28/75
23.做CD⊥AB,D为垂足
acosB=BD=3 bsinA=CD=4
a^2=BD^2+CD^2=25 ∴ a=5
S=AB*CD/2=(BD+AD)CD/2=10
[3+√(b^2-16)]4/2=10 b=2√5
c=AB=3+√(b^2-16)=5或1
l=a+b+c=10+2√5或6+2√5