Which of the following must be true in order to write a bi-conditional statement? A.) the conditional statement
B.) both the conditional statement and its converse
C.) the converse of the conditional statement
D.) neither the conditional statement nor its converse

B.) both the conditional statement and its converse .

Explanation: In order to create a bi-conditional statement, you first need to write a conditional statement and then write the converse of that conditional statement. Finally, you use the if and only if statement structure to combine the conditional statement and its converse.

1. 180°. the sum of the interior angles of a triangle is 180°, for the equilateral triangle that it has three equals side is 60°+60°+60°=180°.

2. 60°. each interior angle of a equilateral triangle is 60°

3. 120°. the measure of ∠m is 120°, the sum of the angles ∠m and ∠n is equal to 180°. so, in order to find the measure of ∠m, we have ∠m+∠n=180° > ∠m=180°-∠n > ∠m=180°-60°=120°.

4. 360°. the sum of the exterior angles of an equilateral triangle is ∠m+∠r+∠x=120°+120°+120°=360°. the exterior angles of any triangle always add 360°.