# A geometry problem by Darius B

**Geometry**Level 2

Given are two linear functions \(f(x)={ m }_{ f }⋅x\) and \(g(x)={ m }_{ g }⋅x\) with \({ m }_{ f },{ m }_{ g }\in ℝ\setminus \left\{ 0 \right\} \). The lines \(f(x)\) and \(g(x)\) are perpendicular to each other on their graph. Find the value of \({ m }_{ f }⋅{ m }_{ g }\)