Distance of (x0,y0)(x_0, y_0)(x0,y0) from ax+by+c=0ax + by + c = 0ax+by+c=0: ∣ax0+by0+c∣a2+b2\dfrac{|ax_0 + by_0 + c|}{\sqrt{a^2 + b^2}}a2+b2∣ax0+by0+c∣. Angle: tanθ=∣m1−m21+m1m2∣\tan\theta = \left|\dfrac{m_1 - m_2}{1 + m_1 m_2}\right|tanθ=1+m1m2m1−m2.