Question

Find the value of x in the given below triangles.

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Answer 1

i) angle 1 = 60°

angle 2 = 70°

angle 3 = x°

=> x° = 180° - ( 60° + 70° )

=> x° = 180° - 130°

=> x° = 50°

ii) angle 1 = 30°

angle 2 = 90°

angle 3 = x°

=> x° = 180° - ( 30° + 90° )

=> x° = 180° - 120°

=> x° = 60°

iii) angle 1 = 40°

angle 2 = 40°

angle 3 = x°

=> x° = 180° - ( 40° + 40° )

=> x° = 180° - 80°

=> x° = 100°

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Answer 2

Required to find :-

• The value of " x " ?

Concept used :-

• In a triangle sum of all angles is supplementary

• The word " supplementary " stands for 180°

Property used :-

• Angle sum property

Solution :-

Figure ( i )

Given angles ;

60° & 70°

By using sum angle property

60° + 70° + x = 180°

130° + x = 180°

x = 180° - 130°

x = 50°

Therefore,

Value of ' x ' is 50°

$\rule{400}{2}$

Figure ( ii )

Given angles ;

30° & 90°

( Since it is a right angled triangle one angle should be a right angle )

By using sum angle property

30° + 90° + x = 180°

120° + x = 180°

x = 180° - 120°

x = 60°

Therefore,

Value of ' x ' is 60°

$\rule{400}{4}$

Figure ( iii )

Given angles ;

40° & 40°

By using right angle property ,

40° + 40° + x = 180°

80° + x = 180°

x = 180° - 80°

x = 100°

Therefore,

Value of ' x ' = 100°

Additional Information :-

1. Types of triangles ;

• 1. Equilateral triangle ( all sides equal )

• 2. Isosceles triangle ( Any two sides are equal )

• 3. Scalene triangle ( All sides have different measures )

2. Other property in a triangle is ;

• Exterior angle property

3. Exterior angle property states that exterior angle is equal to the sum of two opposite interior angles .