Question

Find the distance from (4,2) to the line defined

Answer 1

Answer:

The desired distance is √5

Step-by-step explanation:

Recall that the distance from a point to a line is measured along a path perpendicular to the line.  Thus, given the line y = -2x + 5, the slope of any line perpendicular to it is the negative reciprocal of -2:  +1/2.

The line perpendicular to y = -2x + 5 and passing through (4, 2) is

y - 2 = (1/2)(x - 4), or

2y - 4 = x - 4, or 2y = x, or y = (1/2)x.

Now our problem becomes "find the length of the line connecting (4, 2) and the intersection of y = -2x + 5 and y = (1/2)x."  

Equating these, we get (1/2)x = -2x + 5, which, if multiplied through by 2, becomes x = -4x + 10, or 5x = 10, or x = 2.  If x = 2, then y = (1/2)(2) = 1.

Finally, find the distance between (2, 1) and (4, 2):

Using the Pythagorean Theorem, d = √(2^2 + 1^2) = √5

The distance from (4, 2) to the line y = -2x + 5 is √5