(Ⅰ)求cosB;
(Ⅱ)若a+c=6,△ABC面积为2,求b.
(Ⅰ)求点P的轨迹方程;
(Ⅱ)设点Q在直线x=﹣3上,且 • =1.证明:过点P且垂直于OQ的直线l过C的左焦点F.
(Ⅰ)求c;
(Ⅱ)设D为BC边上一点,且AD⊥AC,求△ABD的面积.
(I)求c的值;
(Ⅱ)求△ABC的面积.
(Ⅰ)求角B的值;
(Ⅱ)若b= ≤a,求2a﹣c的取值范围.
(Ⅰ)求C;
(Ⅱ)若c= ,△ABC的面积为 ,求△ABC的周长.
(Ⅰ)求cosB的值;
(Ⅱ)若点D在线段BC上,且BD=6,c=5,求△ADC的面积.
(Ⅰ)求B;
(Ⅱ)若b= ,求( ﹣1)a+2c的最大值.
(Ⅰ)求sin∠BCE的值;
(Ⅱ)求CD的长.
(Ⅰ)求角B的大小;
(Ⅱ)求 sinA+sin(C﹣ )的取值范围.
(Ⅰ)求∠A的大小;
(Ⅱ)若a= ,且sinA+sin(B﹣C)=2sin2C,求△ABC的面积.