若锐角a,b满足cosa=4/5,cos(a+b)=3/5,则sinb=?
来源:学生作业帮 编辑:搜搜做题作业网作业帮 分类:数学作业 时间:2024/07/28 22:29:44
若锐角a,b满足cosa=4/5,cos(a+b)=3/5,则sinb=?
![若锐角a,b满足cosa=4/5,cos(a+b)=3/5,则sinb=?](/uploads/image/z/17698609-1-9.jpg?t=%E8%8B%A5%E9%94%90%E8%A7%92a%2Cb%E6%BB%A1%E8%B6%B3cosa%3D4%2F5%2Ccos%EF%BC%88a%2Bb%EF%BC%89%3D3%2F5%2C%E5%88%99sinb%3D%3F)
cosa=4/5,sina=3/5
cos(a+b)=cosacosb-sinasinb
3/5=4/5cosb-3/5sinb
3=4cosb-3sinb
(3+3sinb)^2=16cos^2b=16(1-sin^2b)
9+18sinb+9sin^b=16-16sin^2b
25sin^2b+18sinb-7=0
(25sinb-7)(sinb+1)=0
sinb=7/25 sinb=-1(舍去)
cos(a+b)=cosacosb-sinasinb
3/5=4/5cosb-3/5sinb
3=4cosb-3sinb
(3+3sinb)^2=16cos^2b=16(1-sin^2b)
9+18sinb+9sin^b=16-16sin^2b
25sin^2b+18sinb-7=0
(25sinb-7)(sinb+1)=0
sinb=7/25 sinb=-1(舍去)
已知ab均为锐角,若cosa=4/5,cos(a+b)=3/5,求sinb的值
已知a、b都为锐角,cosa=4/5,sinb=5/13,求cos(a-b)的值
已知cosa+cosb=3/5,sina+sinb=4/5,则cos(a-b)
已知cosa+cosb=3/5,sina+sinb=4/5,求cos(a+b)
a,b为锐角,cos(a+b)=12/13 cos(2a+b)=4/5 求cosa
已知a、B为锐角,sina=4/5,cos(a+B)=-3/5,求sinB
已知a、B都是锐角sina=4/5,cos(a+b)=-12/13,求sinB
已知cos(a-b)=3/1,求(sina+sinb)(sina+sinb)+(cosa+cosb)(cosa+cosb
若根号3(sina=sinb)=cosb-cosa,且a,b均为锐角,则a+b=
若根号3(sina+sinb)=cosb-cosa,且a,b均为锐角,则a+b=
已知A,B为锐角,cosA=4/5,tan(A-B)=-1,求cos((A+B)/2)*cos((A-B)/2)的值
若cosa=1/3,sinb=-4/5,且a,b∈(3π/2,2π),则cos(a+b)=