We will construct the angle of 120 degree with help of a compass. Compass is one of the drawing tools which are used in mathematics Geometry. Compass can be used to draw angle of 120 degree.

Let us see how we can construct an angle of 120 degree

Step 1: First of all mark a dot on sheet. Draw a Circle using compass.

Step 2: Place the ruler over circle. Now edge of ruler must be passing through the Centre of circle. Mark a dot where ruler touches circumference of circle.

Step 3: Once again make sure that radius of compass is same as before, it should not change. Mark another Point where line drawn by ruler cuts the circumference. We make another circle on that point with help of ruler.

Step 4: Draw a line from the centre of first circle to the points of second circle. This point of second circle crosses the centre of first circle. These points will create a triangle with equal angles. All sides will have angle of 60 degrees between them and the angle between these two lines is of 120 degrees.

This is the method of constructing angle of 120 degrees without using protractor. There other methods also for constructing 120 degree angles but this method is easier as compared to other methods.