proof help

Question

prove that the perpendicular is the shortest line segment joining an external point to a line.

Answer 1

we don't really need to say 'perpendicular' because the distance from a point to a line always means the shortest distance.)

This is a great problem because it uses all these things that we have learned so far:

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The distance from a point (m, n) to the line Ax + By + C = 0 is given by: