Question

A new library, L, is to be built at some point along a straight road, R, such that its distance from train station, T, is the shortest possible. The train station and the road are placed on a coordinate system where T has coordinates (80, 140) and R has equation y = x - 80. All coordinates are given in kilometers. Find the coordinates of the new library.

Answer 1

Coordinates of the new library is (150, 70)

Explanation:

To get the shortest possible distance means that line from point T to point R has to be perpendicular.

Now, the equation of R is given as;

y = x - 80 - - - (1)

For T to be perpendicular, it means it will have a slope equal to the negative reciprocal of line R.

Thus, slope of T is -1/1 = - 1

Thus, using line - slope intercept of y = mx + c, we can find equation of T as;

140 = -1(80) + c

140 = -80 + c

c = 140 + 80

c = 220

Thus, equation is;

y = -x + 220 - - - (eq 2)

Adding equation 1 to equation 2,we have;

y + y = 220 - 80

2y = 140

y = 140/2

y = 70

Putting 70 for y in eq 1 gives;

70 = x - 80

x = 70 + 80

x = 150

Thus;

Coordinate of the new library is (150, 70)