Given LM = 6.5 cm (using set square)

Construction:
1. Draw a line segment LM = 6.5 cm. Take a point P anywhere above the line LM.
2. Place the set square on the line LM.
3. Draw a line through the point P meeting LM at Q.
4. The line PQ is perpendicular to the line LM at Q. That is, PQ \(\perp\) LM

Given AB = 7 cm

Construction:
1. Draw a line segment AB =7 cm and take a point P anywhere on the line.
2. Place the set square on the line AB.
3. Draw a line PQ through P.
4. The line PQ is perpendicular to the line AB at P. That is PQ f \(\perp\) AB

The sum of three angles = 80°+ 30°+ 40° = 150° (not equal to 180°)
In a triangle, the sum of three angles is 180°.
So, a triangle cannot be formed with the given angles.

Isoceles right angled Triangle
Two angles are equal and one angle is right angle.
Therefore the three angles are 45^o, 45^o, 90^o.

All angles are equal.
I am an equilateral triangle.

i)
 
All sides are equal.
Type: Equilateral triangle.
ii) 

Three sidesare different lengths,
Type: Scalene triangle .
iii)

Two sides are equal,
Type : Isoceles triangle.
iv)
 
Three sides are different lengths.
Type: Scalene triangle.

(i) 80°, 60° 
The sum of 3 angles of triangle = 180° 
Let A = 80° , B = 60° , C = ?
A + B + C = 180° 
80° + 60° + C = 180° 
= 180° - (80° + 60°)
C = 180° - 140° = 40° 
Therefore third angle = 40° 
(ii) 75°, 35°
The sum of 3 angles of triangle = 180° 
Let A = 75°, B = 35°, C = ?
A + B + C = 180° 
75° + 35° + C = 180° 
= 180° - (75° + 35°)
C = 180° - 110° = 70° 
Therefore third angle = 70° 
(iii) 52°, 68°
The sum of 3 angles of triangle = 180° 
Let A = 52°, B = 68°, C = ?
A + B + C = 180° 
52 + 68 + C = 180° 
= 180° - (52° + 68°)
C = 180° - 120° = 60° 
Therefore third angle = 60° 
(iv) 50°, 90°
The sum of 3 angles of triangle = 180° 
Let A = 50°, B = 90°, C = ?
A + B + C = 180° 
50° + 90° + C = 180° 
= 180°  - (50° + 90°)
C = 180° - 140° = 40°
Therefore third angle = 40°
(v) 120°, 30° 
The sum of 3 angles of triangle = 180°
Let A = 120°, B = 30°, C = ?
A + B + C = 180°
75° + 35° + C = 180°
= 180° - (120°+ 30°)
C = 180° - 150 = 30°
Therefore third angle = 30°
(vi) 55°, 85°
The sum of 3 angles of triangle = 180°
Let  A = 55°, B = 85°, C = ?
A + B + C = 180°
55° + 85° + C = 180°
= 180° - (55° + 85°)
C = 180° - 140°= 40°
Therefore third angle = 40°

(i) 60°, 60°, 60° 
The sum of the three angles of a triangle = 180° 
Sum of three angles = 60°  + 60° + 60° = 180°  degrees
Yes, a triangle can be formed.
Type: Acute angled triangle.
(ii) 90°, 55°, 35° 
The sum of three angles of a triangle = 90° + 55° + 35° = 180° 
Yes, a triangle can be formed.
Type: Right angled triangle.
(iii) 60°, 40°, 42°
The sum of three angles of a triangle = 180° 
Sum of the angles = 60°  + 40° + 42°  = 142° 
No a triangle cannot be formed.
(iv) 60°, 90°, 90°
The sum of three angles of a triangle = 180° 
Sum of the angles = 60°  + 90° + 90° 
= 240° \(\neq\) 180° 
No a triangle cannot be formed.
(v) 70°, 60°, 50°
The sum of three angles of a triangle = 180° 
Sum of the angles = 70° + 60° + 50°  = 180°  = 180° .
Yes, a triangle can be formed.
Type: Acute angled triangle.
(vi) 100°, 50°, 30°
The sum of three angles of a triangle = 180° 
Sum of the angles = 100° + 50° + 30° 
= 180° = 180° 
Yes, a triangle cannot be formed.
Type: Obtuse angled triangle