Final answer:
To find the equation of the line perpendicular to AB and passing through (1,2), first find the slope of AB and then take the negative reciprocal to find the slope of the perpendicular line. Use the point-slope form of a linear equation to write the equation of the perpendicular line.
Step-by-step explanation:
To find the equation of a line perpendicular to AB and passing through the point (1,2), we need to first find the slope of AB. The slope of AB can be found using the formula m = (By - Ay) / (Bx - Ax), where (Ax, Ay) and (Bx, By) are the coordinates of points A and B respectively. After finding the slope of AB, we can determine the slope of the line perpendicular to AB by taking the negative reciprocal of the slope of AB. Let's say the slope of AB is m. Then, the slope of the line perpendicular to AB is -1/m. Finally, we can use the point-slope form of a linear equation, y - y1 = m(x - x1), where (x1, y1) is the point through which the line passes, to find the equation of the line perpendicular to AB passing through (1,2).