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Find the acute angle between the lines 3x+2y+4=0 and 2x-3y-7=0.
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| written 6.3 years ago by |
Solution:
For 3x+2y+4=0
$slope m_{1} = \frac{-a}{b} = \frac{-3}{2}$
For 2x-3y-7=0,
$slope m_{2} = \frac{-a}{b} = \frac{-2}{-3} = \frac{2}{3}$ \begin{aligned} \therefore \tan \theta &=\left|\frac{m_{1}-m_{2}}{1+m_{1} m_{2}}\right| \ &=\left|\frac{\frac{-3}{2}-\frac{2}{3}}{1+\left(\frac{-3}{2}\right)\left(\frac{2}{3}\right)}\right| \end{aligned}
$\therefore \tan \theta=\infty$
$\therefore \theta=\tan ^{-1}(\infty)$
$\therefore \theta=90^{\circ} \quad or \quad \frac{\pi}{2}$