二次函数y=1⼀6(x+2根号3)^2的图像的顶点为A,与y轴交于B,以AB为边在第二象限内作等边三角形ABC。

2024-12-15 15:45:32
推荐回答(5个)
回答1:

(1)二次函数的图象的顶点A(-2根号 3 ,0),与y轴的交点B(0,2),
设直线AB的表达式为y=kx+b(k≠0),
得 k=根号3/3,b=2.所以直线AB的表达式为y=根号3/3X+2.
易得∠BAO=30°,∵∠BAC=60°,∴∠CAO=90°.
在Rt△BAO中,由勾股定理得:AB=4.
∴AC=4.点C(-2根号3,4).

(2)∵点C、M都在第二象限,且△ABM的面积等于△ABC的面积,
∴CM∥AB.∴设直线CM的表达式为y=根号3/3x+m,点C在直线CM上,可得 m=6.
∴直线CM的表达式为y=根号3/3x+6.可得点M的坐标:(-5根号3,1).

(3)由C、M坐标可得【两点间距离公式】CM=6
① 当⊙C与⊙N外切时,CN=CM+1=7;
在Rt△CAN中,AN=根号33
∴ON=AN+OA=根号33 +2根号3或ON=AN-OA=根号33-2根号3
即:点N的坐标为:(-根号33-2根号3,0),(根号33-2根号3,0)
②当⊙C与⊙N内切时,CN=CM-1=5;
在Rt△CAN中,CN=5,CA=4,则AN=3;
∴ON=AN+OA=3+2根号3或ON=OA-AN=2根号3-3
即:点N的坐标为:(-3-2根号3,0),(3-2根号3,0)

综上所述,点N的坐标(-根号33-2根号3,0),(根号33-2根号3,0),(-3-2根号3,0),(3-2根号3,0)

回答2:

y=根号3x/3+2 c(-2√3,4)
M(-5√3,1)
N(-2√3+√33,0)或(-2√3-√33,0)

回答3:

1)已知抛物线的解析式,其顶点以及函数图象与y轴交点坐标易求得.在求点C的坐标时,要把握住Rt△AOB的特殊性(含30°角),显然,若△ABC是等边三角形,那么AC与x轴垂直,无论通过勾股定理求边长还是根据B点在AC的中垂线上,都能比较容易的求出点C的坐标.
(2)“M点在第二象限内”确定了点M的大致范围,若“△ABM的面积等于△ABC的面积”,以AB为底边进行分析,那么点C、点M到直线AB的距离是相同的,即CM∥AB,直线AB的解析式易求,两直线平行则斜率相同,再代入点C的坐标就能通过待定系数法求出直线CM的解析式,然后代入点M的纵坐标即可得出结论.
(3)首先求出⊙C的半径,即CM的长.若⊙C与⊙N相切,就要分两种情况来考虑:①外切,CN长等于两圆的半径和;②内切,CN长等于两圆的半径差.
在明确CN长的情况下,在Rt△CAN中,通过勾股定理求出AN的长,进一步即可确定点N的坐标.

回答4:

(1) A(-2√3,0),B(0,2)所以直线方程为y=x/√3+2 ,易知C(-2√3,4)
(2) 由M到直线AB的距离等于C到AB的距离,据点到直线的距离公式易得M(-5√3,1)或M(3√3,1)(舍)
(3) CM=6,设N(x,0),两圆可能外切也可能内切。
由相切两圆的圆心距与半径的关系知:外切时有CN=CM+1=7即(x+2√3)^2+4^2=7^2,
解得x=-2√3+√33或x=-2√3-√33即N(-2√3+√33,0)或(-2√3-√33,0)
内切时有CN=CM-1=5即(x+2√3)^2+4^2=5^2,
解得x=-2√3+3或=-2√3-3即N(-2√3+3,0)或(-2√3-3,0)

回答5:

N(-2√3+√33,0)或(-2√3-√33,0)
M(-5√3,1)

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