Use the Formula $\tan \psi = \left| \frac { m _ { 2 } - m _ { 1 } } { 1 + m _ { 1 } m _ { 2 } } \right|$

Essay

Use the formula $\tan \psi = \left| \frac { m _ { 2 } - m _ { 1 } } { 1 + m _ { 1 } m _ { 2 } } \right|$ to find the acute angle $\psi$ formed by the two lines $y - x = 0$ and $2 x - 3 y = 1$ .