The circumcentre of the triangle formed by the lines \(\mathrm{x}+\mathrm{y}=0, \mathrm{x}-\mathrm{y}=0\) and \(\mathrm{x}-7=0\) is \(\ldots \ldots\) (a) \((7,0)\) (b) \((3.5,0)\) (c) \((0,7)\) (d) \((3.5,3.5)\)

Short Answer

Expert verified
The circumcentre of the triangle formed by the lines $\mathrm{x}+\mathrm{y}=0, \mathrm{x}-\mathrm{y}=0$ and $\mathrm{x}-7=0$ is $(3.5, -3.5)$.

Step by step solution

01

Find the vertices of the triangle

To find the vertices, we need to solve the given linear equations in pairs: 1. x + y = 0 and x - y = 0 2. x + y = 0 and x - 7 = 0 3. x - y = 0 and x - 7 = 0 Solving the first pair of equations, we get: x = 0 and y = 0, which give us the first vertex A(0, 0). Solving the second pair of equations, we get: x = 7 and y = -7, which give us the second vertex B(7, -7). Solving the third pair of equations, we get: x = 7 and y = 7, which give us the third vertex C(7, 7).
02

Calculate the midpoints and slopes of two sides

Consider two sides AB and AC. Find the midpoints of these two sides: Midpoint of AB, M1 = \(\left(\frac{A_x + B_x}{2}, \frac{A_y + B_y}{2}\right)\) = \(\left(\frac{0+7}{2}, \frac{0-7}{2}\right)\) = \((3.5, -3.5)\) Midpoint of AC, M2 = \(\left(\frac{A_x + C_x}{2}, \frac{A_y + C_y}{2}\right)\) = \(\left(\frac{0+7}{2}, \frac{0+7}{2}\right)\) = \((3.5, 3.5)\) Find the slopes of the sides AB and AC: Slope of AB, m1 = \(\frac{B_y - A_y}{B_x - A_x}\) = \(\frac{-7-0}{7-0}\) = \(-1\) Slope of AC, m2 = \(\frac{C_y - A_y}{C_x - A_x}\) = \(\frac{7-0}{7-0}\) = \(1\)
03

Find the perpendicular bisectors of the two chosen sides

The slope of the line perpendicular to AB is the negative reciprocal of m1: m3 = \(\frac{1}{1}\) = \(1\). The slope of the line perpendicular to AC is the negative reciprocal of m2: m4 = \(\frac{1}{-1}\) = \(-1\). Now, we have the slopes and midpoints of the perpendicular bisectors M1R1 and M2R: Equation of M1R1: y - M1_y = m3 (x - M1_x) ⇒ y - (-3.5) = 1(x - 3.5) ⇒ y + 3.5 = x - 3.5 Equation of M2R: y - M2_y = m4 (x - M2_x) ⇒ y - 3.5 = -1(x - 3.5) ⇒ y - 3.5 = -x + 3.5
04

Calculate the intersection point of the two perpendicular bisectors

To find the circumcentre, we need to solve the two equations obtained in Step 3: 1. y + 3.5 = x - 3.5 2. y - 3.5 = -x + 3.5 Add both equations: 2y = -7 y = -3.5 Substitute the value of y in the first equation: -3.5 + 3.5 = x - 3.5 0 = x - 3.5 x = 3.5 Hence, the circumcentre is (3.5, -3.5), which is not among the given options.

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