When two lines meet, they can intersect in different ways. The most special case is when lines are perpendicular, meaning they meet at exactly 90 degrees. This creates a right angle, which we mark with a small square symbol.
Not all intersecting lines are perpendicular. When two lines meet at any angle other than 90 degrees, we call them oblique intersecting lines. The angle can be acute, like 45 degrees, or obtuse, like 120 degrees. Only when the angle is exactly 90 degrees do we call the lines perpendicular.
To identify perpendicular lines, look for these key indicators: First, the right angle symbol - a small square at the intersection point. Second, the angle measurement of exactly 90 degrees. Third, the perpendicular symbol which looks like an upside-down T. Remember, all four angles formed by perpendicular lines are equal - each measuring 90 degrees.
Perpendicular and intersecting lines are everywhere around us. Graph paper shows perfect perpendicular lines forming a grid. Window frames have perpendicular crossbars. The plus sign is made of two perpendicular lines. Scissors show intersecting lines at an angle. Clock hands can be perpendicular when showing 3 o'clock or 9 o'clock. These examples help us recognize these geometric relationships in everyday objects.
Let's summarize the key differences. Perpendicular lines always meet at exactly 90 degrees and form equal angles. They have a special right angle symbol and perpendicular symbol. Intersecting lines can meet at any angle, forming unequal angles with no special symbols. Remember this important rule: all perpendicular lines are intersecting lines, but not all intersecting lines are perpendicular. Perpendicular is just a special case of intersection.