Key Points - Constructions

- Basic Constructions
- Some Constructions of Triangles

(1) Use only ruler and compass while drawing constructions.
(2) Protractor may be used for drawing non-standard angles.
(3) Constructions of a triangle given its base. a base angle and the difference of the other two sides.
(4) Constructions of a triangle given its perimeter and its two base angles.
(5) A triangle can be constructed if its perimeter and two base angles are given. 
(6) Geometrical construction is the process of drawing a geometrical figure using only two instruments-an ungraduated ruler and a pair of compasses. 
(7) Some specific angles like 15°.30°. 45°. 60°. 75°. 90° . etc. can be constructed without using protractor. 
(8) A triangle can be constructed if its base. base angle and the sum of the two sides or the difference of the other two sides are given.