# Perpendicular Lines ## Perpendicular Lines

Two line segments are said to be perpendicular lines if the angle between them is 90°.
In the given figure, ACD = BCD = 90°, so the line segments AB and CD are perpendicular. It is written as ABCD and read as AB perpendicular to CD or vice-versa.

### Construction of a perpendicular line using a set square

To construct a perpendicular line to a given line, we follow the following steps:
Step 1: Draw a line PQ of the given measurement and take a point M.
Step 2: Hold the ruler firmly along the line PQ.
Step 3: Place a set square with its shortest side against the ruler at M.
Step 4: Slide the set square firmly till the perpendicular edge is on the point M.
Step 5: Draw a line MN along the perpendicular edge of the set square. Then MN is the perpendicular to PQ at M.

### Construction of a perpendicular from a point by using a compass

To construct a perpendicular by using compass, we follow the following steps:
Step 1: Draw a line segment AB and take any point C above AB.
Step 2: Draw an arc PQ on the line segment AB from the point C.
Step 3: Draw arcs from the points P and Q below AB so that two arcs intersect and join the point C and intersection point or arcs.
CD is perpendicular to AB i.e.CDAB.

### Construction of a perpendicular at a point of the given line by using a compass

To construct a perpendicular at a point of the given line by using a using a compass, we follow the following steps:
Step 1: Draw a line segment AB. Take any point C on the line segment AB.
Step 2: Fix the compass needle at point C and draw an arc at C and level one point M as shown in the figure. Without changing the span of the compass, cut two arcs from point M and level it putting the compass needle at M to P and from P and level it Q.
Step 3: Putting the needle of the compass at P and Q, draw two arcs so that they intersect at D as shown in the figure. Join the points C and D.
CD is perpendicular to AB i.e.CDAB.

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