Comparing ‌3y2−8xy−3x2−29x+3y−18=0 ‌ with ‌ax2+2hxy+by2+2gx+2fy+c=0 ‌‌‌‌‌a=3,b=−3 3y2−8xy−3x2−29x+3y−18=0 with ax2+2hxy+by2+2gx+2fy+c=0 Here, ‌‌a=3,b=−3 a ‌‌b=0 ⇒ Lines are perpendicular. Hence, angle between the lines =‌