Question

if two angles of triangle are 30° and 40° respectively. then find measure of third angle of triangle.​

Answer 1

Required Answer :

The third angle of triangle = 110°

Given :

Two angles of a triangle :-

• First angle = 30°
• Second angle = 40°

To find :

• The measure of the third angle of triangle

Solution :

Let,

• The third angle of triangle = x

Using formula,

• Sum of interior angles of polygon = (2n - 4) × 90°

where,

• n = number of sides

Triangle has 3 sides, 3 angles.

⇒ Number of sides (n) = 3

Substituting the given values :

⇒ 30° + 40° + x = (2 × 3 - 4) × 90°

⇒ 70° + x = (6 - 4) × 90°

⇒ 70° + x = 2 × 90°

⇒ 70° + x = 180°

⇒ x = 180° - 70°

⇒ x = 110°

Therefore, the third angle of triangle = x = 110°

Answer 2

Answer:

The third angle of triangle is 110°.

Explanation:

Given,

two angles of a triangle = 30° and 40°

to find: measure of third angle

according to angle sum property of triangle,

the sum of the three angles of a triangle is 180°

This can be proved by following formula,

sum of angles = (2n-4) × 90°

n = number of sides

we are talking about triangles so it has three sides, n = 3

sum of angles = [2(3)-4] × 90°

2 × 90° = 180°

so,

let the third angle be x

30° + 40° + x = 180°

70° + x = 180°

x = 180° - 70°

x = 110°

Hence, the third angles of triangle is 110°