# Angle between two intersecting lines

Geometry Level 2

Let $$l$$ be the line that is perpendicular to the $$xy$$-plane and passes through the point $$(2, 1, -3).$$ Let $$m$$ be the line that is perpendicular to the $$x$$-axis and passes through the same point $$(2, 1, -3).$$ Find the value of $$\cos {\theta} ,$$ where $$\theta$$ is the acute angle between $$l$$ and $$m.$$

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