Find the angle between the x-axis and the line joining the points (3, –1) and (4, –2).
Find the angle between the x-axis and the line joining the points (3, –1) and (4, –2).

 Slope of the line joining the focuses \[\left( \mathbf{3},\text{ }-\text{ }\mathbf{1} \right)\text{ }\mathbf{and}\text{ }\left( \mathbf{4},\text{ }-\text{ }\mathbf{2} \right)\]  is given by

 

\[\mathbf{m}\text{ }=\text{ }\left( \mathbf{y2}\text{ }\text{ }\mathbf{y1} \right)/\left( \mathbf{x2}\text{ }\text{ }\mathbf{x1} \right)\] where, \[\mathbf{x}\text{ }\ne \text{ }\mathbf{x1}\]  

\[\mathbf{m}\text{ }=\text{ }\left( -\text{ }\mathbf{2}\text{ }\text{ }\left( -\text{ }\mathbf{1} \right) \right)/\left( \mathbf{4}-\mathbf{3} \right)\]

\[=\text{ }\left( -\text{ }\mathbf{2}+\mathbf{1} \right)/\left( \mathbf{4}-\mathbf{3} \right)\]

\[=\text{ }-\text{ }\mathbf{1}/\mathbf{1}\]

\[=\text{ }-\text{ }\mathbf{1}\]

 point of tendency of line joining the focuses \[\left( \mathbf{3},\text{ }-\text{ }\mathbf{1} \right)\text{ }\mathbf{and}\text{ }\left( \mathbf{4},\text{ }-\text{ }\mathbf{2} \right)\]  is given by

\[\mathbf{tan}\text{ }\mathbf{\theta }\text{ }=\text{ }-\text{ }\mathbf{1}\]

\[\mathbf{\theta }\text{ }=\text{ }\left( \mathbf{90}{}^\circ \text{ }+\text{ }\mathbf{45}{}^\circ  \right)\text{ }=\text{ }\mathbf{135}{}^\circ \]

The point between the x-pivot and the line joining the focuses \[\left( \mathbf{3},\text{ }\text{ }\mathbf{1} \right)\text{ }\mathbf{and}\text{ }\left( \mathbf{4},\text{ }\text{ }\mathbf{2} \right)\]  is \[\mathbf{135}{}^\circ .\]