Math

Question Find the equation of a circle with center at (3,6)(-3, 6) given that the line 3xy5=03x - y - 5 = 0 is tangent to the circle.

Studdy Solution

STEP 1

Assumptions
1. The equation of the line tangent to the circle is 3xy5=03x - y - 5 = 0.
2. The center of the circle is (3,6)(-3,6).
3. The radius of the circle is the perpendicular distance from the center of the circle to the tangent line.
4. The general equation of a circle with center (h,k)(h,k) and radius rr is (xh)2+(yk)2=r2(x-h)^2 + (y-k)^2 = r^2.

STEP 2

First, we need to find the perpendicular distance from the center of the circle to the tangent line. This distance will be the radius of the circle.

STEP 3

The distance dd from a point (x0,y0)(x_0, y_0) to a line Ax+By+C=0Ax + By + C = 0 is given by the formula:
d=Ax0+By0+CA2+B2d = \frac{|Ax_0 + By_0 + C|}{\sqrt{A^2 + B^2}}

STEP 4

Plug in the values for the center of the circle (3,6)(-3,6) and the coefficients of the line 3xy5=03x - y - 5 = 0 into the distance formula.
d=3(3)1(6)532+(1)2d = \frac{|3(-3) - 1(6) - 5|}{\sqrt{3^2 + (-1)^2}}

STEP 5

Calculate the numerator of the distance formula.
Numerator=3(3)65=965=20=20Numerator = |3(-3) - 6 - 5| = |-9 - 6 - 5| = |-20| = 20

STEP 6

Calculate the denominator of the distance formula.
Denominator=32+(1)2=9+1=10Denominator = \sqrt{3^2 + (-1)^2} = \sqrt{9 + 1} = \sqrt{10}

STEP 7

Now, calculate the distance dd, which is the radius of the circle.
d=2010=20101010=201010=210d = \frac{20}{\sqrt{10}} = \frac{20}{\sqrt{10}} \cdot \frac{\sqrt{10}}{\sqrt{10}} = \frac{20\sqrt{10}}{10} = 2\sqrt{10}

STEP 8

Now that we have the radius of the circle, we can write the equation of the circle using the general form.

STEP 9

Substitute the center of the circle (3,6)(-3,6) and the radius 2102\sqrt{10} into the general equation of a circle.
(x(3))2+(y6)2=(210)2 (x - (-3))^2 + (y - 6)^2 = (2\sqrt{10})^2

STEP 10

Simplify the equation of the circle.
(x+3)2+(y6)2=410 (x + 3)^2 + (y - 6)^2 = 4 \cdot 10

STEP 11

Further simplify the equation of the circle by expanding the right side.
(x+3)2+(y6)2=40 (x + 3)^2 + (y - 6)^2 = 40

STEP 12

The equation of the circle in standard form is:
(x+3)2+(y6)2=40 (x + 3)^2 + (y - 6)^2 = 40
This is the final equation of the circle with center (3,6)(-3,6) that is tangent to the line 3xy5=03x - y - 5 = 0.

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