Construct an obtuse angled triangle which has a base of 5.5 cm and base angles of 30° and 120°.

The steps are as follows:

1. Draw a line BC of side 5.5 cm

2. Construct 120° at point B and draw a straight line through it and extend the ray Y.

3. Draw an angle of 30° at point C and extend the ray X.

4. Extend BY and CX in such manner that they intersect to get the third point A.

5. Join AC to complete the triangle.

Steps to construct 120°:

1. Use ruler and draw a Line segment OB of any convenient length.

2. Now use compass and open it to any convenient radius. And with O as center, draw an arc which cuts line segment OB at X.

3. Again use compass and opened to the same radius (as of step 2). And with X as center, draw an arc which cuts first arc at D.

4. Again use compass and opened to the same radius (as of step 2). And with D as center, draw another arc which cuts first arc at C.

5. Join OC which is 120° line.

Steps to construct 30°:

1. Use ruler and draw a Line segment OB of any convenient length.

2. Now use compass and open it to any convenient radius. And with O as center, draw an arc which cuts line segment OB at X.

3. Again use compass and opened to the same radius (as of step 2). And with X as center, draw an arc which cuts first arc at D.

4. Now keep the compass distance same and from point D draw an arc and from point X draw an arc. The two arcs will coincide to give 30° line.

5. Draw a line from O to intersection of two arcs.