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If the line $y=2 x+c$ is a tangent to the circle $x^2+y^2=5$, then a value of $c$ is
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Verified Answer
The correct answer is:
5
Here, $\quad m=2$ and $c_1=c$
Given equation of circle is
$x^2+y^2=5$
Here radius $a=\sqrt{5}$
Since, the line (i) is tangent to the circle.
$\begin{aligned}
& \therefore \quad c=a \sqrt{m^2+1}=\sqrt{5} \sqrt{(2)^2+1} \\
& \Rightarrow \quad c=\sqrt{5} \cdot \sqrt{5}=5 \\
&
\end{aligned}$
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