Question

Given the diagram below, Gitta writes mZ1 + m 2 + m/3 = 180°. Which of

the following reasons allows her to write this statement?
O
A. Exterior angles theorem
O
B. Triangle sum theorem
O
C. Subtraction property of equality
O
D. Definition of linear pair

Answer 1

Option B:

Triangle sum theorem allows her to write the statement.

Solution:

Gitta writes m∠1 + m∠2 + m∠3 = 180°

To find which reason allows her to write this statement:

∠1, ∠2 and ∠3 are interior angles of the triangle.

Triangle sum theorem:

Sum of all the interior angles of the triangle is 180°.

⇒ m∠1 + m∠2 + m∠3 = 180°

Hence triangle sum theorem allows her to write the above statement.

Option B is the correct answer.