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在△ABC中,若,则cosC的值为A.B.C.D.
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在△ABC中,若
![](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAJEAAAAjCAYAAACU2uhdAAAAAXNSR0IArs4c6QAAAARnQU1BAACx
jwv8YQUAAAAgY0hSTQAAeiYAAICEAAD6AAAAgOgAAHUwAADqYAAAOpgAABdwnLpRPAAAA29JREFU
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8ASB5cniuXYioCIZSRgOxtdlkWGYL9tOUgUKL32wVWMsf1bGj8hLEyTRzrdTIfG7UHDyqAclIc5p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)
,则cosC的值为( )
A.
![](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAC0AAAAjCAYAAAAAEIPqAAAAAXNSR0IArs4c6QAAAARnQU1BAACx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)
B.
![](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAA8AAAAjCAYAAABLuFAHAAAAAXNSR0IArs4c6QAAAARnQU1BAACx
jwv8YQUAAAAgY0hSTQAAeiYAAICEAAD6AAAAgOgAAHUwAADqYAAAOpgAABdwnLpRPAAAAQ1JREFU
SEvVVQEOwyAIdF/2O/zEd/gKP0FVtMBE25olS02WLKUHxwnXD+bjdk8B7x63C6yMT3AK6J3HkCbp
atzlFvkdAkcofauATJGCN2OCdkSwKtfEgNEgdAFOGLxDgM4s/xdZ1uBWFSIhvukvwfVlH5A1LK1x
9YdgasO3K7lFm9tsGrQHtwRzXaWigWiDwOcAlLvWiuYhqH3SHOgr+9F4bgz5HyuTEM9/eiXf1bNi
a7gFb1PTZZgwY904aZ4wtVkcETZku0WxKGkAkmkGr9yCYtZc01VduEWvFGE0SHflFoOLih4MsHYL
PTtavJP2zC0GsKzcBZu5hQRH0F+UtpITt1g6jPxWvXgxHlI/ADp+Bd9zZp+gAAAAAElFTkSuQmCC
)
C.
![](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAA8AAAAjCAYAAABLuFAHAAAAAXNSR0IArs4c6QAAAARnQU1BAACx
jwv8YQUAAAAgY0hSTQAAeiYAAICEAAD6AAAAgOgAAHUwAADqYAAAOpgAABdwnLpRPAAAASFJREFU
SEvVlY0JxCAMhb2VXSebOIdTuEROTdTEaAU5KCeUFvTl56lfP5iHux1FfDvcrbBW3MQp+FI+PT5g
mqOmgL7Oeww8yeKIsBJwAAo8RC0uiSMgxE0Dec45wNV0FicMnss1i2gOoASgNTKJMiyC7qlUVLJC
pLxz+cbtuoDD12/lRfZGZF9s1TDPiqkNz3avxa0xYxZ7wO4ZcQS5JWymDCbacNkF3nzrJm0e9Ulu
6y37zfG8OeMvZu43qZvSzHl+qyv5Zz2rche0GLfJUmbCkKVFPWEbynSS7GjxRJlOkjUtnihT6Hmg
RfPEUKag90QLaaikTD0kJ1row6PN62UPtGpaGLHA50DvhhZSrCnTfzcbWhwo8+J9vrmK+kd3GeEL
YpwCk/cOuQQAAAAASUVORK5CYII=
)
D.
相关试题
-
已知A,B,C为△ABC的三个内角;a,b,c分别为对边,向量
=(2cosC-1,-2),
=(cosC,cosC+1),若
⊥
,且a+b=10,则△ABC周长的最小值为( )
A.10-5![](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAA8AAAASCAYAAACEnoQPAAAAAXNSR0IArs4c6QAAAARnQU1BAACx
jwv8YQUAAAAgY0hSTQAAeiYAAICEAAD6AAAAgOgAAHUwAADqYAAAOpgAABdwnLpRPAAAALtJREFU
OE/Nk9sVhCAMRENH9EMXFEET9EAB1ME59pAmsgmPFRF15Wv5UuQymUlUxAuGpZQat+bvAo+LT862
z+f+HMZIlq2IHfDpW+zU3NFzIm8jYUb4mS9o/DOMWMEimPwbuE80+bdl74oLnjvpGpyNJYFnz8Mg
YLQENUCgYEoLwOwtuJuwzjeEEDLkNJB2WynnEkaKdpZ2rqCoH2BRagPS9fjk2fBHUV/6MTanCbRb
g6UUUV9SbnH/Cn8A/r2EUaEPy7EAAAAASUVORK5CYII=
)
B.10+5![](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAA8AAAASCAYAAACEnoQPAAAAAXNSR0IArs4c6QAAAARnQU1BAACx
jwv8YQUAAAAgY0hSTQAAeiYAAICEAAD6AAAAgOgAAHUwAADqYAAAOpgAABdwnLpRPAAAALtJREFU
OE/Nk9sVhCAMRENH9EMXFEET9EAB1ME59pAmsgmPFRF15Wv5UuQymUlUxAuGpZQat+bvAo+LT862
z+f+HMZIlq2IHfDpW+zU3NFzIm8jYUb4mS9o/DOMWMEimPwbuE80+bdl74oLnjvpGpyNJYFnz8Mg
YLQENUCgYEoLwOwtuJuwzjeEEDLkNJB2WynnEkaKdpZ2rqCoH2BRagPS9fjk2fBHUV/6MTanCbRb
g6UUUV9SbnH/Cn8A/r2EUaEPy7EAAAAASUVORK5CYII=
)
C.10-2![](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAA8AAAASCAYAAACEnoQPAAAAAXNSR0IArs4c6QAAAARnQU1BAACx
jwv8YQUAAAAgY0hSTQAAeiYAAICEAAD6AAAAgOgAAHUwAADqYAAAOpgAABdwnLpRPAAAALtJREFU
OE/Nk9sVhCAMRENH9EMXFEET9EAB1ME59pAmsgmPFRF15Wv5UuQymUlUxAuGpZQat+bvAo+LT862
z+f+HMZIlq2IHfDpW+zU3NFzIm8jYUb4mS9o/DOMWMEimPwbuE80+bdl74oLnjvpGpyNJYFnz8Mg
YLQENUCgYEoLwOwtuJuwzjeEEDLkNJB2WynnEkaKdpZ2rqCoH2BRagPS9fjk2fBHUV/6MTanCbRb
g6UUUV9SbnH/Cn8A/r2EUaEPy7EAAAAASUVORK5CYII=
)
D.10+2
-
已知A,B,C为△ABC的三个内角;a,b,c分别为对边,向量
=(2cosC-1,-2),
=(cosC,cosC+1),若
⊥
,且a+b=10,则△ABC周长的最小值为( )
A.10-5![](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAA8AAAASCAYAAACEnoQPAAAAAXNSR0IArs4c6QAAAARnQU1BAACx
jwv8YQUAAAAgY0hSTQAAeiYAAICEAAD6AAAAgOgAAHUwAADqYAAAOpgAABdwnLpRPAAAALtJREFU
OE/Nk9sVhCAMRENH9EMXFEET9EAB1ME59pAmsgmPFRF15Wv5UuQymUlUxAuGpZQat+bvAo+LT862
z+f+HMZIlq2IHfDpW+zU3NFzIm8jYUb4mS9o/DOMWMEimPwbuE80+bdl74oLnjvpGpyNJYFnz8Mg
YLQENUCgYEoLwOwtuJuwzjeEEDLkNJB2WynnEkaKdpZ2rqCoH2BRagPS9fjk2fBHUV/6MTanCbRb
g6UUUV9SbnH/Cn8A/r2EUaEPy7EAAAAASUVORK5CYII=
)
B.10+5![](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAA8AAAASCAYAAACEnoQPAAAAAXNSR0IArs4c6QAAAARnQU1BAACx
jwv8YQUAAAAgY0hSTQAAeiYAAICEAAD6AAAAgOgAAHUwAADqYAAAOpgAABdwnLpRPAAAALtJREFU
OE/Nk9sVhCAMRENH9EMXFEET9EAB1ME59pAmsgmPFRF15Wv5UuQymUlUxAuGpZQat+bvAo+LT862
z+f+HMZIlq2IHfDpW+zU3NFzIm8jYUb4mS9o/DOMWMEimPwbuE80+bdl74oLnjvpGpyNJYFnz8Mg
YLQENUCgYEoLwOwtuJuwzjeEEDLkNJB2WynnEkaKdpZ2rqCoH2BRagPS9fjk2fBHUV/6MTanCbRb
g6UUUV9SbnH/Cn8A/r2EUaEPy7EAAAAASUVORK5CYII=
)
C.10-2![](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAA8AAAASCAYAAACEnoQPAAAAAXNSR0IArs4c6QAAAARnQU1BAACx
jwv8YQUAAAAgY0hSTQAAeiYAAICEAAD6AAAAgOgAAHUwAADqYAAAOpgAABdwnLpRPAAAALtJREFU
OE/Nk9sVhCAMRENH9EMXFEET9EAB1ME59pAmsgmPFRF15Wv5UuQymUlUxAuGpZQat+bvAo+LT862
z+f+HMZIlq2IHfDpW+zU3NFzIm8jYUb4mS9o/DOMWMEimPwbuE80+bdl74oLnjvpGpyNJYFnz8Mg
YLQENUCgYEoLwOwtuJuwzjeEEDLkNJB2WynnEkaKdpZ2rqCoH2BRagPS9fjk2fBHUV/6MTanCbRb
g6UUUV9SbnH/Cn8A/r2EUaEPy7EAAAAASUVORK5CYII=
)
D.10+2
-
已知△ABC中,(b+a)(sinB-sinA)=asinB,又cos2C+cosC=1-cos(A-B).
(I)试判断△ABC的形状;
(II)求cosC的值.
-
已知△ABC的内角A,B,C的对边分别为a,b,c,其中c=2,又向量
=(1,cosC),
=(cosC,1),
•
=1.
(1)若A=45°,求a的值;
(2)若a+b=4,求△ABC的面积.
-
已知△ABC的内角A,B,C的对边分别为a,b,c,其中c=2,又向量
=(1,cosC),
=(cosC,1),
•
=1.
(1)若A=45°,求a的值;
(2)若a+b=4,求△ABC的面积.
-
已知△ABC的内角A,B,C的对边分别为a,b,c,其中c=2,又向量
=(1,cosC),
=(cosC,1),
•
=1.
(1)若A=45°,求a的值;
(2)若a+b=4,求△ABC的面积.
-
已知△ABC的内角A,B,C的对边分别为a,b,c,其中c=2,又向量
=(1,cosC),
=(cosC,1),
•
=1.
(1)若A=45°,求a的值;
(2)若a+b=4,求△ABC的面积.
-
已知△ABC的内角A,B,C的对边分别为a,b,c,其中c=2,又向量
=(1,cosC),
=(cosC,1),
•
=1.
(1)若A=45°,求a的值;
(2)若a+b=4,求△ABC的面积.
-
在锐角△ABC中,角A,B,C所对的边分别为a,b,c,已知向量
=(2b-c,cosC),
=(a,cosA),且
∥
,
(Ⅰ)求角A的大小;
(Ⅱ)求cosB+cosC的取值范围.
-
已知在△ABC中,BC=1,B=
,当△ABC的面积等于
时,cosC=________.