If [tex]\(A\left(x_1, y_1\right), B\left(x_2, y_2\right), C\left(x_3, y_3\right)\)[/tex], and [tex]\(D\left(x_4, y_4\right)\)[/tex] form two line segments, [tex]\(\overline{AB}\)[/tex] and [tex]\(\overline{CD}\)[/tex], which condition needs to be met to prove [tex]\(\overline{AB} \perp \overline{CD}\)[/tex]?

A. [tex]\(\frac{y_1-y_3}{x_4-x_3} \times \frac{y_1-y_1}{x_3-x_1}=1\)[/tex]

B. [tex]\(\frac{y_1-y_1}{y_2-x_1}+\frac{x_4-x_3}{x_3-x_1}=0\)[/tex]

C. [tex]\(\frac{y_1-y_3}{x_1-x_3} \times \frac{y_2-y_1}{x_3-x_1}=-1\)[/tex]

D. [tex]\(\frac{y_2-y_1}{x_4-x_1}-\frac{x_1-x_1}{y_4-y_3}=1\)[/tex]

E. [tex]\(\frac{y_1-y_2}{y_2-x_1}+\frac{x_1-x_2}{x_2-x_1}=0\)[/tex]



Answer :

To determine if the two line segments [tex]\(\overline{AB}\)[/tex] and [tex]\(\overline{CD}\)[/tex] are perpendicular, we need to use the concept of slopes. The slopes of two lines are perpendicular if the product of their slopes is [tex]\(-1\)[/tex].

1. Calculate the slope of [tex]\(\overline{AB}\)[/tex]:
The slope of a line segment [tex]\(\overline{AB}\)[/tex] connecting points [tex]\(A(x_1, y_1)\)[/tex] and [tex]\(B(x_2, y_2)\)[/tex] is given by:
[tex]\[ \text{slope}_{AB} = \frac{y_2 - y_1}{x_2 - x_1} \][/tex]

2. Calculate the slope of [tex]\(\overline{CD}\)[/tex]:
The slope of a line segment [tex]\(\overline{CD}\)[/tex] connecting points [tex]\(C(x_3, y_3)\)[/tex] and [tex]\(D(x_4, y_4)\)[/tex] is given by:
[tex]\[ \text{slope}_{CD} = \frac{y_4 - y_3}{x_4 - x_3} \][/tex]

3. Check if the product of the slopes is [tex]\(-1\)[/tex]:
For the two line segments to be perpendicular, their slopes must satisfy:
[tex]\[ \text{slope}_{AB} \times \text{slope}_{CD} = -1 \][/tex]
Substituting the respective slopes, we get:
[tex]\[ \left( \frac{y_2 - y_1}{x_2 - x_1} \right) \times \left( \frac{y_4 - y_3}{x_4 - x_3} \right) = -1 \][/tex]

4. Simplify the condition:
Simplifying the above condition, it can be written as:
[tex]\[ \frac{(y_2 - y_1) \times (y_4 - y_3)}{(x_2 - x_1) \times (x_4 - x_3)} = -1 \][/tex]
Rearranging, we obtain:
[tex]\[ (y_2 - y_1) \times (y_4 - y_3) = - (x_2 - x_1) \times (x_4 - x_3) \][/tex]

Among the given options, the correct condition that matches this analysis is option [tex]\( \text{C}\)[/tex]:
[tex]\[ \frac{y_2 - y_1}{x_2 - x_1} \times \frac{y_4 - y_3}{x_4 - x_3} = -1 \][/tex]

Therefore, the correct answer is:
[tex]\[ \boxed{3} \][/tex]