Answer: A. 4
Step-by-step explanation:
The characteristic equation of a circle is
[tex]x^2+y^2=r^2[/tex]
The characteristic equation of a hyperbola is
[tex]\frac{x^2}{a^2}-\frac{y^2}{b^2}=1[/tex]
The intersection points will be obtained as the solution of the both characteristic equations.
[tex]x^2+y^2=r^2[/tex].......(1)
[tex]\frac{x^2}{a^2}-\frac{y^2}{b^2}=1[/tex].............(2)
⇒[tex]y^2=r^2-x^2[/tex].....(from 1)
put this in (2)
[tex]\frac{x^2}{a^2}-\frac{r^2-x^2}{b^2}=1[/tex]
⇒[tex]y^2=r^2-x^2\\\frac{x^2}{a^2}+\frac{-x^2}{b^2}=1+\frac{r^2}{b^2}[/tex]
⇒[tex]y^2=r^2-x^2\\x^2(\frac{1}{a^2}+\frac{1}{b^2})=1+\frac{r^2}{b^2}[/tex]
⇒[tex]y^2=r^2-x^2\\x^2(\frac{a^2+b^2}{a^2b^2})=\frac{b^2+r^2}{b^2}[/tex]
[tex]\Rightarrow\ x^2=\frac{a^2(b^2+r^2)}{a^2+b^2}\\y^2=\frac{b^2(r^2-a^2)}{a^2+b^2}[/tex]
So there are 2 different values of x and two different values of y, thus the maximum number of intersection points is 4.
