### Theory:

There are many places where we are see the perpendicular lines and parallel lines in our real life.

Just check out the following collage.

Let us discuss the perpendicular cases:
• The sides of the soccer field with the centre lines
• Television screen with its edges
• Some grills in the window design
• Railway track crossing
• Sign of the first aid kit
Let us check the definition of perpendicular line with an example:
Two different lines intersecting each other at right angle or $$90°$$ are called perpendicular lines.

Let us check some more examples:

Let us discuss some of the parallel cases:
• Lines in the race field
• Railway track
• Cars in the queue
• Steel rack shelves
• Sides of the road
Two lines are parallel when they do not intersect each other at any point on the plane.
Set Square:
Two triangular instruments in the geometry box are called as 'Set square'.
• Both the set squares has right angles in it.
• One of the set squares is an isosceles triangle with two angles measuring $$45°$$ on the equal sides.
• Other set square is a scalene triangle with two angle measuring $$30°$$ and $$60°$$.

Uses of Set square:
• To construct the specific angles $$90°$$, $$45°$$, $$30°$$ and $$60°$$.
• To draw parallel and perpendicular lines.
• To measure the height.