Bisecting Angles

Construction of Bisecting Angles
Using a protractor draw are angle of measure 80⁰.Bisect the given angle.

Step 1: Draw a ray OA.

Step 2:With the help of protractor draw an angle AOB of measure 80⁰
Step 3: With center O and a convenient radius draw an arc cutting arms OA and OB at P and Q respectively.

Step 4: With center P and radius more than half-length of PQ, draw an arc.

Step 5: With center Q and same radius as in the step 4, draw another arc intersecting the arc drawn in the step 4 at R.

Step 6: Join OR and Produce it to form a ray OX the angle AOX is the angle of measure 40⁰ ( one half of 80⁰)


Construction of Angles 60⁰,120⁰and 180⁰

Step 1 : Draw a line segment AB of any length.

Step 2 : Draw an arc of any radius with center A, which cuts AB at P.

Step 3 : With same radius and center at P draw another arc, which cuts earlier arc at Q.

Step 4 : Join AQ.

Step 5 : ∠BAD = 60⁰

Step 4 : With same radius and centre at Q draw another arc which cut the first arc at R.

Step 5 : Join A and R by drawing AC.

Step 6 : ∠CAB is the required 120° angle.

Geometrical Constructions

• Basic Geometric Constructions
• Construction of Line Segment
• Bisecting a Line Segment
• Constructing Angles
• Bisecting Angles
• Constructing Parallel Lines
• Construction of Triangle (SSS)
• SAS Triangle Construction
• ASA Triangle Construction
• HL Triangle Construction (Rhs -construction)
• Constructing Quadrilaterals
• Constructing Triangles(when sum of sides or perimeter is given)