# Smallest Acute angle.

Geometry Level 3

Find the acute angle between the pair of lines given below,

$$\left( l^{ 2 }\quad -\quad 3m^{ 2 } \right) x^{ 2 }\quad +\quad 81mxy\quad +\quad \left( m^{ 2 }\quad -\quad 3l^{ 2 } \right) y^{ 2 }\quad =\quad 0$$

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