To find the equation of the circle passing through the points (1, √3), (1, -√3), and (3, -√3), we can follow these steps:
### Step 1: General Equation of the Circle
The general equation of a circle can be expressed as:
\[ x^2 + y^2 + 2gx + 2fy + c = 0 \]
where \( g \), \( f \), and \( c \) are constants that we need to determine.
### Step 2: Substitute the First Point (1, √3)
Substituting the point (1, √3) into the equation:
\[
1^2 + (\sqrt{3})^2 + 2g(1) + 2f(\sqrt{3}) + c = 0
\]
This simplifies to:
\[
1 + 3 + 2g + 2\sqrt{3}f + c = 0
\]
\[
4 + 2g + 2\sqrt{3}f + c = 0 \quad \text{(Equation 1)}
\]
### Step 3: Substitute the Second Point (1, -√3)
Now, substituting the point (1, -√3):
\[
1^2 + (-\sqrt{3})^2 + 2g(1) + 2f(-\sqrt{3}) + c = 0
\]
This simplifies to:
\[
1 + 3 + 2g - 2\sqrt{3}f + c = 0
\]
\[
4 + 2g - 2\sqrt{3}f + c = 0 \quad \text{(Equation 2)}
\]
### Step 4: Subtract Equation 2 from Equation 1
Subtracting Equation 2 from Equation 1:
\[
(4 + 2g + 2\sqrt{3}f + c) - (4 + 2g - 2\sqrt{3}f + c) = 0
\]
This simplifies to:
\[
4\sqrt{3}f = 0
\]
Thus, we find:
\[
f = 0
\]
### Step 5: Substitute \( f = 0 \) into Equation 1
Substituting \( f = 0 \) into Equation 1:
\[
4 + 2g + c = 0 \quad \text{(Equation 3)}
\]
### Step 6: Substitute the Third Point (3, -√3)
Now, substituting the point (3, -√3):
\[
3^2 + (-\sqrt{3})^2 + 2g(3) + 2f(-\sqrt{3}) + c = 0
\]
This simplifies to:
\[
9 + 3 + 6g + c = 0
\]
\[
12 + 6g + c = 0 \quad \text{(Equation 4)}
\]
### Step 7: Substitute \( c \) from Equation 3 into Equation 4
From Equation 3, we have \( c = -4 - 2g \). Substitute this into Equation 4:
\[
12 + 6g + (-4 - 2g) = 0
\]
This simplifies to:
\[
12 - 4 + 4g = 0
\]
\[
8 + 4g = 0
\]
Thus, we find:
\[
g = -2
\]
### Step 8: Find \( c \)
Substituting \( g = -2 \) back into Equation 3:
\[
4 + 2(-2) + c = 0
\]
\[
4 - 4 + c = 0 \implies c = 0
\]
### Step 9: Write the Final Equation of the Circle
Now we have:
- \( g = -2 \)
- \( f = 0 \)
- \( c = 0 \)
Substituting these values into the general equation:
\[
x^2 + y^2 + 2(-2)x + 2(0)y + 0 = 0
\]
This simplifies to:
\[
x^2 + y^2 - 4x = 0
\]
### Step 10: Rearranging the Equation
Rearranging gives:
\[
x^2 - 4x + y^2 = 0
\]
Completing the square for \( x \):
\[
(x - 2)^2 - 4 + y^2 = 0 \implies (x - 2)^2 + y^2 = 4
\]
### Final Answer
The equation of the circle is:
\[
(x - 2)^2 + y^2 = 4
\]