已知M(x,y)是圆x^2+y^2=1上任意一点,求y/(x+2)的取值范围
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你好!
用换元法,设t=y/(x+2)
y=t(x+2)代入x^2+y^2=1中
得:x^2+t^2(x+2)^2=1
x^2+t^2*x^2+4t^2*x+4t^2=1
(1+t^2)x^2+4t^2*x+4t^2-1=0
判别式必须满足△=(4t^2)^2-4*(1+t^2)(4t^2-1)>=0
16t^4-4[4t^2-1+4t^4-t^2]>=0
4-12t^2>=0
t^2<=1/3
-根号3/3<=t<=根号3/3
即y/(x+2)的范围为[-根号3/3,根号3/3]
哪里不清欢迎追问,满意谢谢采纳!
用换元法,设t=y/(x+2)
y=t(x+2)代入x^2+y^2=1中
得:x^2+t^2(x+2)^2=1
x^2+t^2*x^2+4t^2*x+4t^2=1
(1+t^2)x^2+4t^2*x+4t^2-1=0
判别式必须满足△=(4t^2)^2-4*(1+t^2)(4t^2-1)>=0
16t^4-4[4t^2-1+4t^4-t^2]>=0
4-12t^2>=0
t^2<=1/3
-根号3/3<=t<=根号3/3
即y/(x+2)的范围为[-根号3/3,根号3/3]
哪里不清欢迎追问,满意谢谢采纳!
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解:设x=cosa y=sina 则:M=y/(x+2) = cosa/(sina+2)
cosa=Msina+2M
即:2M = cosa-Msina = √(M^2+1)sin[a+arctan(1/M)]
2M(max) = √(M^2+1)
即:4M^2 = M^2+1
M = ± √3/3
∴y/(x+2)的取值范围为:[ -√3/3,√3/3 ]
cosa=Msina+2M
即:2M = cosa-Msina = √(M^2+1)sin[a+arctan(1/M)]
2M(max) = √(M^2+1)
即:4M^2 = M^2+1
M = ± √3/3
∴y/(x+2)的取值范围为:[ -√3/3,√3/3 ]
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