1.设x>0,则函数y=x+(2/2x+1)+1的最小值是________2.在△ABC中,BC=a,AC=b,a,b是方程x²-2根号3x+2=0的两根且2cos(A+B)=1,则AB=____3.在锐角三角形ABC中,满足a²sin(A+B)=(a²+c²-b²)sin(A+C)且C≠B(1)若B
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![1.设x>0,则函数y=x+(2/2x+1)+1的最小值是________2.在△ABC中,BC=a,AC=b,a,b是方程x²-2根号3x+2=0的两根且2cos(A+B)=1,则AB=____3.在锐角三角形ABC中,满足a²sin(A+B)=(a²+c²-b²)sin(A+C)且C≠B(1)若B](/uploads/image/z/2654578-10-8.jpg?t=1.%E8%AE%BEx%EF%BC%9E0%2C%E5%88%99%E5%87%BD%E6%95%B0y%3Dx%2B%282%2F2x%2B1%29%2B1%E7%9A%84%E6%9C%80%E5%B0%8F%E5%80%BC%E6%98%AF________2.%E5%9C%A8%E2%96%B3ABC%E4%B8%AD%2CBC%3Da%2CAC%3Db%2Ca%2Cb%E6%98%AF%E6%96%B9%E7%A8%8Bx%26%23178%3B-2%E6%A0%B9%E5%8F%B73x%2B2%3D0%E7%9A%84%E4%B8%A4%E6%A0%B9%E4%B8%942cos%28A%2BB%29%3D1%2C%E5%88%99AB%3D____3.%E5%9C%A8%E9%94%90%E8%A7%92%E4%B8%89%E8%A7%92%E5%BD%A2ABC%E4%B8%AD%2C%E6%BB%A1%E8%B6%B3a%26%23178%3Bsin%28A%2BB%29%3D%28a%26%23178%3B%2Bc%26%23178%3B-b%26%23178%3B%29sin%28A%2BC%29%E4%B8%94C%E2%89%A0B%EF%BC%881%EF%BC%89%E8%8B%A5B)
1.设x>0,则函数y=x+(2/2x+1)+1的最小值是________2.在△ABC中,BC=a,AC=b,a,b是方程x²-2根号3x+2=0的两根且2cos(A+B)=1,则AB=____3.在锐角三角形ABC中,满足a²sin(A+B)=(a²+c²-b²)sin(A+C)且C≠B(1)若B
1.设x>0,则函数y=x+(2/2x+1)+1的最小值是________
2.在△ABC中,BC=a,AC=b,a,b是方程x²-2根号3x+2=0的两根且2cos(A+B)=1,则AB=____
3.在锐角三角形ABC中,满足a²sin(A+B)=(a²+c²-b²)sin(A+C)且C≠B
(1)若B,C所对的边为b,c求b/b+c的范围
4已知平面上的动点Q到顶点F(0,1)的距离与它到直线y=3的距离相等,求动点Q的轨迹方程
1.设x>0,则函数y=x+(2/2x+1)+1的最小值是________2.在△ABC中,BC=a,AC=b,a,b是方程x²-2根号3x+2=0的两根且2cos(A+B)=1,则AB=____3.在锐角三角形ABC中,满足a²sin(A+B)=(a²+c²-b²)sin(A+C)且C≠B(1)若B
第一题:y=(x+1/2)+1/(x+1/2)+1/2>=2+1/2.等号成立的条件是x+1/2=1/(x+1/2),结合x>0,知,x=1/2.所以y的最大值就是5/2.
第二题:a+b=2根号3,ab=2.a^2+b^2=(a+b)^2-2ab=8.由题目中另一个条件推知cosC=-1/2=(a^2+b^2-c^2)/2ab.解得c=3.就是AB=3.
第三题:首先,可把等式化为a^2sinC=(a^2+c^2-b^2)sinB,记此式为(一).sinC=c/2r,sinB=b/2r,r为三角形外接圆半径.代入化简可得到a^2(c-b)=b(c-b)(c+b),由于B不等于C,所以b-c不等于0.所以a^2=b(b+c).b/(b+c)=b^2/a^2=(sinB/sinA)^2.
另外在一式两边同时除以2ac,根据余弦定理和正玄定理可得到sinA=sin2B.把此式带入上式得到b/(c+b)=(1/4)*(secB)^2,而0
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