To draw an angle of $35°$, we should place the protractor and mark $35$ degree as shown below.

 

Draw some more angles measuring clockwise and anticlockwise.

(i) A line segment is a portion of a line. If $A$ and $B$ are two points in a plane, the part $AB$ of the line through $A$ and $B$ is called a line segment $\left(AB\right)$. The points $A$ and $B$ are called the endpoints of this segment.

(ii) A line segment has two end points, and a line has no end points.

(iii) There is a unique line segment joining two given points $A$ and $B$.

(iv) The line segment $\left(AB\right)$ is the same as the line segment $\left(BA\right)$.

(v) The length of a line segment $\left(AB\right)$ is denoted by $AB$.

(vi) Two or more line segments having the same length are said to be congruent or equal.

(vii) The distance between two points is the same as the length of the line segment joining these points.

2. Unit Conversions:

(i) $1 \mathrm{m}=100 \mathrm{cm}; 1$ yards $=3 \mathrm{ft}$

(ii) $1 \mathrm{cm}=10 \mathrm{mm}; 1 \mathrm{ft}=12$ inches

(iii) $1 \mathrm{km}=1000 \mathrm{m}; 1$ mile $=1760$ yards

3. Ray:

(i) The part of a line that extends indefinitely in one direction from a given point $\mathrm{O}$, is called a ray. The point $\mathrm{O}$ is called the initial point or the endpoint of the ray.

(ii) OA→ and AO→ are two different rays.

(iii) A ray has only one end point.

(iv) An unlimited number of rays can be drawn with the same initial point.

(v) A unique ray can be drawn from a given initial point and passing through a given point.

(vi) A ray has no definite length.

4. Mathematical Instruments to Construct Shapes:

(i) A graduated ruler

(ii) The compasses

(iii) The divider

(iv) Set-squares

(v) The protractor

5. Constructions Using the Ruler and Compass:

(i) A Circle when the length of its radius is known.

(ii) A Line Segment if its length is given.

(iii) A copy of a Line Segment.

(iv) A perpendicular to a line through a point

(a) on the line

(b) not on the line.

(v) The perpendicular bisector of a line segment of given length.

(vi) An angle of a given measure.

(vii) A copy of an angle.

(viii) The bisector of a given angle.

(ix) Some angles of special measures:

(a) $90°$

(b) $45°$

(c) $60°$

(d) $30°$

(e) $120°$

(f) $135°$