已知a∈(0,π),且sina cosa=m(0
来源:学生作业帮助网 编辑:作业帮 时间:2024/09/30 05:39:18
1.a∈(0,π/2),2a∈(0,π)sin(2a)>0sin(2a)=√[1-cos²(2a)]=√[1-(4/5)²]=3/5a∈(0,π/2),sina>0cosa>0si
|a+b|^2=|a|^2+|b|^2+2a·b=1+2-2√2sinα+sinα^2+cosα^2+2cosα(√2-sinα)+2sinαcosα=4+2√2(cosα-sinα)=4+4cos(
sina+cosa=1/5sin^2a+cos^2a=1sin^2a+(1/5-sina)^2=12sin^2a-2sina/5+1/25=12sin^2a-2sina/5-24/25=050sin^
sinA+cosA=7/13……(1)(sinA+cosA)^2=49/1691+2sinAcosA=49/169sinAcosA=-60/169……(2)由(1)(2),得sinA=12/13cos
(1)(sina+cosa)^2+(sina-cosa)^2=2因为a属于(0,π/2)所以sina+cosa>0sina+cosa=7/5因为sina+cosa=1/5所以sina=4/5cosa=
可得:sin(a-π/3)=√5/3sina=sin[(a-π/3)+π/3]=sin(a-π/3)cosπ/3+cos(a-π/3)sinπ/3=√5/3x1/2+2/3x√3/2=√5/6+2√3
=a/2-(a/2-b)cosa/2=2√5/5cos(a/2-b)=3√10/10sinb=sina/2*cos(a/2-b)-cosa/2*sin(a/2-b)=(√5/5)*(3√10/10)-
因为sina*cosa=60/169=5/13*12/13所以sina=5/13与cosa=12/13或sina=12/13与cosa=5/13
sina+cosa=1/5,且0<a<π由勾股数组3,4,5得:sina=4/5,cosa=-3/5所以,tana=-4/3
sina=3√130/130以下是解题过程:由a∈(π/2,π)和sin(2a-β)>0,知道2a-β∈(0,π/2),所以cos(2a-β)=4/5,cosβ=5/13cos(2a)=cos(2a-
sinA是4/5,cos是-3/5.题目做多了就知道,这个三角数组要当成特殊角记得,很有用.在考试时不要再一步步算,而是列个式子直接给答案,能在高考中争取时间.如果要解就再用方程sinA平方+cosA
6cosa^2-sina-5=06(1-sina^2)-sina-5=06-6sina^2-sina-5=06sina^2+sina-1=0sina=-0.5或者sina=1/3因为a为锐角所以sin
cosa^2=1-sina^2=1-16/25cosa=3/5cos2a=1-2sina^2=1-2*16/25=-7/25
tana=1∴a=π/4∴sina=根号2/2
sina+cosa=tana-1/tanasina+cosa=sina/cosa-cosa/sinasina+cosa=(sin²a-cos²a)/sinacosa1=(sina-
a属于(0,π/4),sina-cosa
向量a//b,则有sina-2cosa=0sina=2cosa(sina)^2+(cosa)^2=15(cosa)^2=10
因为a垂直于b,所以sina+2cosa=0.所以tana=-2所以sina=2/根号5,cosa=-1/根号5所以sina-cosa=2/根号5+1/根号5
sina>0,且cosa
sina>0∴a∈[0,π]cos