Problem

Recall the equation for a circle with center $(h, k)$ and radius $r$. At what point in the first quadrant does the line with equation $y=0.5 x+4$ intersect the circle with radius 6 and center $(0,4)$ ? \[ \begin{array}{l} x= \\ y= \end{array} \] Enter your answer correct to 3 decimal places .

Solution

Step 1 :The equation for a circle with center \((h, k)\) and radius \(r\) is given by \((x-h)^2 + (y-k)^2 = r^2\).

Step 2 :Given that the circle has a center at \((0,4)\) and a radius of 6, the equation of the circle is \((x-0)^2 + (y-4)^2 = 6^2\), which simplifies to \(x^2 + (y-4)^2 = 36\).

Step 3 :The equation of the line is \(y=0.5x+4\).

Step 4 :Substituting \(y\) into the equation of the circle gives \(x^2 + (0.5x)^2 = 36\), which simplifies to \(x^2 + 0.25x^2 = 36\).

Step 5 :Combining like terms gives \(1.25x^2 = 36\), and solving for \(x\) gives \(x^2 = 36/1.25\).

Step 6 :Taking the square root of both sides gives \(x = \sqrt{36/1.25}\).

Step 7 :Since we are looking for the point in the first quadrant, we take the positive root, so \(x = \sqrt{36/1.25} \approx 5.366\).

Step 8 :Substituting \(x\) into the equation of the line gives \(y = 0.5(5.366) + 4 \approx 6.683\).

Step 9 :So, the point of intersection in the first quadrant is approximately \((5.366, 6.683)\).

Step 10 :Checking the solution, we substitute \(x\) and \(y\) into the equation of the circle and verify that the left-hand side equals the right-hand side, confirming that the solution is correct.

Step 11 :The final answer is \(\boxed{(5.366, 6.683)}\).

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Source: https://solvelyapp.com/problems/pck8SSrHGZ/

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